Frankly, the prices you get are not worth the effort. If Goodwill would take books (other than paperback novels), or if we still had any used book stores, I would donate them, but those options no longer exist in my area.
I'm all for purging. Not as much for the throwing away. As a college student I brought a big box of my RPGs I wouldn't get a chance to play, from Cyborg Commando (Gygax post D&D) to older Champions editons to a friend who ran a different game every night of the week and told him that he and any of his gamer friends could have anything they wanted. I've been doing that since. Most recent with RPG was giving away a large number of my D&D 3.x, 4e, and old AD&D books. Those last were hard because of all the formative memories, but I literally had opened one once in the previous decade, to show the art to one of my kids (who play 5e), so I let them go. It seemed like to a good place as well where students would get to play.
I do the same with physical books. When my shelves get too overflowing (as opposed to normal overflowing) I'll go through and grab all the books I won't be rereading again but are worth reading and let friends at them. My car currently has seven bags of books I bagged up pre-covid and then sat in my spare room. I'll make a trip to my friend who said he wants them over the weekend.
But I'm lucky to have lots of people in my area who game and who share my taste in books so I can pass them on. But just decluttering is a good thing - I'm such a packrat at times.
I don't think I'm as radical as you - I'm not sure how much you are actually throwing away instead of selling or gifting, but that's something I don't consider. Still, I sold 1/3 of my physical collection over the last years, and am currently planning to sell off about the same number of books (the last batch will probably take a bit longer).
And in general I agree with you: as much as I like the energy of a good in-person game, I don't see that coming back. And with solid tablets, PDFs and a growing number of VTTs, online games are the best chance for me to keep playing (I have had more sessions in the last 2 years than in the 5 years before). And they also greatly increase the chance to play something else than the most popular systems.
I still have files of my old campaigns. Maps, character sketches from a player who now is a pro comic artist, the last character sheet from a player who sadly passed away during the campaign.
But I'm a nostalgic sap, so I understand why others don't value things like that.
A few years ago I went through an exercise of scanning all my old notes, character sheets, and the like - 30+ years of personal gaming history. But... while there was some good stuff in there, honestly they wouldn't have been any great loss to the world.