Pretty sure it's not the games that are the problem in most cases. I semi-frequently go through depressive episodes, and it doesn't matter how good the game (or any other hobby) is, I just can't have fun with it
I do feel like there's a high chance a lot of the people complaining about "dead game" or "games just aren't as fun as they used to be anymore" are in fact experiencing either gaming burnout or something else, thinking fondly back on when they used to have fun.
Especially when they're like "I have played 2000 hours of this game and this game isn't fun anymore and is going to die".
Additionally I think it's also just nostalgia and getting older. When I played rollercoaster tycoon when I was younger, the park guests felt alive, I didn't know everything that could be researched yet, and I didn't play to maximize the score. Now I know too much. The guests are just a simple algorithm, everything feels known, and I'm way more focused on actually playing for the objective. I still like RCT, but the magic from those days is gone. As we learn more about the world and get more responsibilities we seem to lose this sense of wonder about everything. Even new games often seem like something you already know, instead of something completely new, just because you've seen so many games already.
That being said, I can personally still get back to that feeling of wonder with the right games. It's not totally as it used to be, but there's still plenty of fun to be had. If I'm in a phase where I keep closing every game I start, I know I'm just not in the right place mentally and it's not because of the games.
It probably is the games though. They're probably playing repetitive addictive online competitive multiplayer games. Doing the same thing every single day with a new skin dangling in front of them to keep them going.
Games are still fun, but they aren't as good as the old ones. Was on Gamescom last sunday, almost every game there you had the feeling you already played it. The indie area was better, but companies make games for money and do not like risks.
When was this magical time where big companies didn't make dog shit games (with exceptions)? We always remember the good ones not the 10000 single player shooters that were 6 hours long or the movie tie-in games we got because as kids we thought they must be as good as the movies.
Heck, I remember reading about Spiderman 2 seemingly being an open world game (in a time where that wasn't widespread or you even called it that) where you complete tasks and swing around an open New York City, only to buy it and recognizing that what I was reading about was the PS2 version, not the PC version. The PC version was a soulless husk of a movie cash grab game. I can say that about dozens of games I played back when I was a kid.
Not every game we got was some timeless classic like Ocarina of Time.
I am talking about games like, stronghold crusader, mount and blade warband (even though it was a buggy mess), tonic trouble, tetris, skyrim (but only thanks to the modding community that fixed it), minecraft.
Yes there is nostalgic involved that blurs my view on the past.
But the only modern games i can think of that are good are Kingdom come, the whicher 3 and Vampire survivor.
The problem is that nowadays we have thousands of games to choose from and most are garbage from AAA to most indie games. It's harder to get a good one. Even though there are probably more good ones than 20 years ago.