In practice, it is not that easy. Changing 5e to 3.5 via houserules would be a pretty massive document. When you advertise for a 5e game, people expect a few houserules. They don't expect AD&D.
This is I think the main problem. If it were easy to find older editions, I doubt so many people would waste time saying what they dislike about 5e. There's such a high level of discontent because 5e is unavoidable. You cannot play rpgs and insulate yourself from it, unless you have a long time group of people with identical interests.
It's tempting to say "well that must mean no one likes old editions, and they have to deal with being unpopular". I think this ignores the importance of network effects. Most players in the community are not posting on enworld. They don't know what chainmail is. They've not heard of skill points. If they spend 4 hours a week gaming, that represents a pretty big time commitment for this hobby, and they don't have the time to evaluate all sorts of other systems. And, they want to play what everyone else is playing.
I have a ton of 3.5 books if anyone wants them! Heck, I have almost everything in .pdf format! And those books mostly collect dust unless I want to adapt something from them or use them as inspiration.
The same goes for 2e, 1e, and even older D&D books- it's not hard to actually play a previous version of a game if you want to. At least, I don't think it is.
The problems are more that 1) not everyone wants to play those versions of the game, and 2) people want to see those versions of the game "fixed"* with updates, without having to do the work themselves (the whole reason we buy books, right? So a professional can do the job for us?).
*Whatever this means for the individual.
But instead, publishers decide to go in some other direction, and getting people to play something they may (rightly or wrongly) see as "old and busted" leaves you with little choice but to embrace the new game- grumbling mightily about the things you don't like. I play and run 5e. I don't want to!
But it's what the people I play with currently want, so I must go where the gaming is. If I had my druthers, we'd be playing 4e, Pathfinder 1e, 3.5, or hell, Earthdawn! But instead, it looks like we'll be switching to Tales of the Valiant. What can you do?
I wish 5e2024 looked more like those games I mentioned, but it's not going to happen any time soon. I can't make it happen, and I'm resigned to that fact.
Every edition/version/variant of D&D has gone in a different direction that the others. Yes, even 2e, despite remaining highly compatible with 1e, veered off into it's own lane. We're seeing that now with the 2014-2024+ split. Expecting things to change now is futile. Expecting people who are fine with the current direction to change their minds, probably equally so.
I wish we lived in a world that, when someone asked me what game I'm playing, I could say "D&D" and not have to clarify which version I'm talking about! But a lot of different factors led us to this point. If, like me, you have to accept it or not find play, I feel for you, but we lack the power to turn the ship now.
Even if we vote with our wallets and protest loudly, it might not happen. We don't have the same broken base as there was with the 4e split. There isn't a lone competitor threatening to take the lion's share of profits in the Fantasy TTRPG space- not yet, at least. The Balkanization of TTRPG's will continue, but D&D will continue to exert a pull, like gravity, on both the market and pop culture.
For now. We don't have to like it, but I think we all have to come to peace with it.