Hope this helps. Like many, I had stopped playing a few years ago, and just came back during the last week of Season 19. I came back confused and asking “How did this go from this to that”, etc.

Maybe it’s because I have autism, but I had to piece everything together for my sanity.

I tried watching a few collective videos, but most seemed to go too fast for me or leave some stuff out.

So what I did was Google the seasons and DLC’s I missed separately, with “story” after them.

Ex: “Destiny 2, Season 18 story” or “Destiny 2, Season of Plunder story”. I found in depth articles explaining the pieces from where I left off. Although you won’t need them all, here is a list of all of the prior seasons:

Season 19: Season of the Seraph Season 18: Season of Plunder Season 17: Season of the Haunted Season 16: Season of the Risen Season 15: Season of the Lost Season 14: Season of the Splicer Season 13: Season of the Chosen Season 12: Season of the Hunt Season 11: Season of Arrivals Season 10: Season of the Worthy Season 9: Season of Dawn Season 8: Season of the Undying Season 7: Season of Opulence Season 6: Season of the Drifter Season 5: Season of the Forge Season 4: Season of the Outlaw Season 3: Warmind Season 2: Curse of Osiris Season 1: Red War

If you want a faster recap, try this page and scroll down past D1 to Destiny 2.

https://tvtropes.org/pmwiki/pmwiki.php/Recap/Destiny