I've so far gone on a near -2000 downswing in MMR on my best heroes (QoP, Tinker, Crystal Maiden). There's a variety of reasons including:

1. Myself misplaying, I recognize I make errors, and a lot of them.
2. There are a lot of smurfs around 3K mmr, maybe 1 out of every 5 games there's someone with a 20 game winstreak 90% winrate on some high micro hero.
3. There is a lot of toxicity at 10K behavior score; not just verbal abuse but gameplay toxicity, intentionally throwing, and my favorite, ping spammers.

I would say my games are probably distributed in a curve like this:

• 15% I carried (either playing/stomping with a core, or doing some amazing saves as support).
• 20% I got carried (played mediocre/bad on either role).
• 5% We all played well.
• 60% We got destroyed through a combination of other team out picking or having better players, we all played poorly, or we had someone who threw the game.

On behavior:

• 35% of my games have some toxic player @ 10K behavior. Often times lately I'm getting international players that just flame in a foreign language while spam pinging.
• Around 20% of games have smurfs.
• Remainder 45% I would say are fair: either we suck, they suck, or we both suck.

I'm a bit older now (busy with prof/social life) so when I sit down to play Dota the last thing I want to do is manage other players like I'm managing clients. Checking my Garmin it tells me my stress levels are higher playing Dota than when running a 5K, winning bar trivia, or in an intense proposal meeting so this is clearly not a healthy lifestyle for me. And that's the big thing, I've spent so much time learning how to play this game, and instead of enjoying it because it's great, it's feeling more and more like "accepting it for what it is".

When you talk law of large numbers, sure if I play 10 games a day, dealing with 3 bad games isn't a big deal, I've got 7 that should be fair. But now it's more like 1 game a day if I'm available, and the first game has a strong chance of being a bad experience.