In my early days of searching for a consistent gaming group, I put in an application for a 5e game on Roll20 that sounded incredible.  The game world was divided into kingdoms, each dedicated to one of the schools of magic.  Magic was a heavy factor on social status, and those without magic affinity were treated as the lowest of the low on the rungs of society.  The setting was very lore-rich and well thought out, so it sounded like it would be an amazing roleplay experience.

The rest of the party were casters of various sorts to fit the high-magic political setting, but I opted to play about as low-magic as it gets: Battlemaster Fighter.  Given the low status of non-magic users, we explained my presence in the party by having me be a bodyguard employed by one of the other players.  Besides, with the abundance of squishy casters, we needed someone that could take a hit and protect the rest.  My character was lawful neutral: following orders and obeying the law, even if the law brought misery to herself or those like her.  Her focus was set firmly on keeping everyone alive.  I hoped that sometime in the future if we came across an NPC being oppressed harshly for their low-magic status, it would be a big character shift for my fighter to break from her normal obedient disposition to come to that person's aid.

Unfortunately I never got the chance as the lore and social structure of the world seemed to go right out the window from the start.  We began the game in a dungeon.  And I don't mean the prison kind, but the kind with puzzles, traps, and treasure.  Okay, we'll probably get into the roleplay world once we've cleared it.

After a relatively easy combat, we found a chest of holding, and a pool of what the DM called 'diamond water'.  As the DM explained it, diamond water would provide additional AC to any armor it coated, and would turn to diamonds if splashed or dripped on a hard surface.  And the pool was about 1000 cubic feet.  We decided to open the new chest of holding at the bottom of the pool, and take it all with us.  So after just an hour of play, we essentially had inifnite money.

Cut to the end of the dungeon, we fight our first boss, which turns out to be a Balor.  Keep in mind, we started the game at level 7, and a Balor is typically CR 19.  The DM pulled a few strings to tone it down a little, but still not an easy fight.  I made heavy use of Goading Attack to keep the boss's attention on me, or give him disadvantage on attacks if he didn't, which caused him to miss several times when going for our squishy casters.  I'm not sure whether it enraged the boss or the DM, but for the rest of the fight, he was focused squarely on me, even when I wasn't goading.

I did not know Balor mechanics, but when a balor dies it explodes for 20d6 damage, which ended up just 10 short of killing me outright when I failed my Dex save.  Everyone else was far enough back that they were fine, and we made it out of the dungeon.  Now we get to the roleplay setting, right?  Nope.  We exited through a portal into a town where the only thing of interest was a store.  We were dismissively discouraged from interacting with anything else in the area.

We went into the store, and the DM linked us to a PDF of the entire magic item lineup from the DMG, which we can purchase with our virtually infinite money worth of diamond water.  On top of that, there were some special homebrew items we could buy.  I didn't really appreciate that we hardly had to work for any of this.  I opted not to buy anything because in the lore of the world non-magic people were not permitted to own magical items.  The DM handwaved this by saying it was fine, my employer would technically own them so I could get whatever I wanted.  I still went light on my purchases and came out of it with a 1 shield that could absorb a spell cast into it and allowed me to re-cast it later.

Once we were done making our purchases, we were teleported against our will to some kind of celestial court, where a group of powerful angels drafted us into collecting several items for them.  We weren't given much choice, and I was still wondering when the lore-rich world will actually come into play.  The angels teleported us back to (wouldn't you guess it) another dungeon.

This time, the dungeon boss was an adult blue dragon, but even without using my maneuvers to draw its attention to me, it seemed remarkably intent on taking me out on its own.  It even went so far as to attack me after taking me to 0 HP, making me fail two death saves from a hit while dying.  Fortunately I succeeded a save on my turn, and our healer got me back up on my feet before another caster took the dragon down.  To our surprise, though, the dragon had the same 20d6 explosion on death that the balor had.  This time I passed my save, but if I had not, the damage would have killed me.  That seemed very odd to me, but we survived it.

After turning in the item that the angels had sent us for, we were sent to yet another dungeon, and now I was finally starting to understand that this was going to just be a dungeon crawl, and the world's lore and social structure was not going to come into play.  The boss this time was a gorgon, and again it seemed particularly focused on me.  I was okay with this, since taking the hits for the party was my role, but it seemed to indicate a pattern.  Fortunately I was rolling REALLY well or I would have been turned to stone with a single failed save.  I asked the DM if I could use my magic shield to absorb the petrifying gaze as a spell, and the DM allowed it, but informed me that it wouldn't work on the Gorgon herself.  "That's fine" I said, and absorbed the spell on my next save.  As expected, the gorgon exploded on death, but I had enough health that a failed save didn't matter, and we were all still alive.

This was getting very repetitive, and while I stuck with the group as it was my only D&D outlet, outside of the game I was looking for a new one.  It was disappointing, but not quite meeting the criteria for the 'Bad D&D is worse than No D&D' rule.  I hadn't signed up for a dungeon crawl, and I wanted a game with more balance between roleplay and combat.

I had to miss the next session, in which we were assigned to capture a person hiding out in, of course, a dungeon.  I informed the DM that if our target didn't go willingly, that I intended to use my stored petrification ability to turn our target to stone for delivery to the angels without a fight.  We were high enough level by now that our healer could reverse this with a Greater Restoration spell upon delivery.

When I came back to the game: Good news, the target had epicly failed his save against my petrify.  Bad news: He attempted a self-destruct and was petrified mid-explosion.  So although we delivered the statue to the angels, they considered him dead because he would explode upon being un-petrified, and so they were extremely disappointed in us.

This pattern continued for at least one more dungeon (it was a while ago, so I don't exactly remember how many) where the boss would do their utmost to kill my character and only mine, but couldn't manage it and would explode as they died as a last ditch effort to finish me off.  And every time, I survived and the whole party remained alive, so I didn't make a big deal out of it.  I got the distinct feeling that DM was trying to kill my character, but not overdo it and kill the whole party in the process.  It is only as I write this up that I realize we had infinite diamonds and could have afforded any kind of resurrection, but I have a feeling the DM would have overruled that in some fashion.

This came to a head in what I think was our first non-dungeon session.  We were sent to a social gathering to find and kill a particular person of interest.  It did not take us long to identify our target, and combat began with probably as little roleplay as possible.  I was still the boss's main target, but the DM was rolling very poorly and not landing a single attack while the rest of the party practically melted him with spells.  Finally, luck caught up with him and he landed a multi-attack with two 21's back to back, which I had calculated as exactly my AC.  The damage was rolled, and I was knocked down to just below 0 HP.

I thought I was fine, but the DM promptly added on "And you're dead."  "What?" I asked, a little taken aback.  "Yeah, this guy has a mindflayer ability that when you are taken down to 0 HP, you are straight-up dead."  It was then that the party came to my rescue, making sure my AC was properly calculated, and sure enough, I had forgotten to include the 1 from my magic shield, so my AC was actually 22 and the attacks missed after all.  The DM seemed very frustrated by this, but allowed combat to continue, which of course ended with the boss exploding in my face.

Before the next session, the DM messaged me privately and told me that the other players had been complaining about my character, so he was removing me from the game.  He then kicked me and blocked me before I could respond.  I have seen stories that end like this be followed up with revelations that the OP is actually a chronic problem player, so I wanted to mention that I reached out to some of the other players for corroboration of the DM's claim, but none of them expressed any problem with me or my character and were equally confused.  I don't know what happened to the party after that.

What disappointed me most is that the DM had created such a great world concept that utterly went to waste.  And to be fair, he had clearly put a lot of work into some well-made dungeons.  I just wish they could have been part of a greater narrative without so much boss bullying.