For games it is twofold. Plus whatever psychology says (most people have their tastes set around about the time they are 19 and will go with that forever more).
I have a hard time with modern games as well, this despite still loving games (I was way past 19 when the 360 hit but I still enjoy many 360 games, gamecube as well) and can't think of what I am going to take away from this generation really, even for the playable enough versions -- I don't care so much for most driving games but got out need for speed underground 2 on my gamecube a while back and had a blast, don't think I will be grabbing a copy of need for speed paycheque or whatever to have as my arcadey driving game of choice for when I want to play such a thing.
1) Computer games are a new endeavour and radically changing quite a bit.
Books is books is books. Music is music is music. Even films is films is films for quite some years now.
Sure the state of the art has moved on a bit, and what can be accomplished on what budget has changed, and in academic settings you can find a bit more still*, but I can watch films from the 50s that are great, and books from far before then that are also great, music possibly further back still and paintings/sculpture still looks great however many thousands of years on we are from some of the great masters.
*while computer games have game theory to fall on as their academic base I can't ignore the story writing lessons around today (see Brandon Sanderson's lectures on writing), the lessons on film making/cinematography and the like, the level of music theory that people are going to now and so on and so on.
Games from the 70s... now that is a bigger ask, and they change radically every 5 or so years up until around the late 360 where it sort of stalled out in terms of level size, mechanics, number of things they ask you to handle, control quality and whatever else.
I don't think this stalling out is a technical limit (though we are probably within sight of something like one) but it might have contributed at some level.
2) Yeah computer game companies seem to have opted out of making games that might flop and instead just go for safe, widest market (which often means lowest common denominator) and thus bland, possibly while trying to reach into my wallet to ask me to pay for things that were previously always part of the game. Or indeed have what would have previously been incredibly thin games; perfect dark N64 had
https://gamefaqs.gamespot.com/n64/198275-perfect-dark/faqs/8345 how many multiplayer maps, whole bunch of modes in each of those, bots to play with, challenges within the maps, and a fully fleshed out story (also co-op)... Now I am lucky to get 6 maps all of which will be "three lanes" because "that is what games are".
I would not care but they seem to spent ridiculous sums of money on development, way above any rate of inflation (all the while the hardware is getting faster and thus making their job theoretically even easier), and still get left wanting.
The age of the b tier game seems to have come to a close, now it was probably during the PS2 that it happened but there was enough life left in it to stagger on through the PS360. That is usually what gave us our monster titles, cult classics, or otherwise uncovered new developers for us (other than maybe PS4 Spiderman, and that is Spiderman during what has to be the biggest point for comic book films in decades, has there been a surprise hit outside of seriously indy games in recent years?). Even most of the interesting devs buggered off to android and IOS when they hit towards the end of the DS' lifetime which means Nintendo consoles have also been lacking for me.
I wish I could understand when DANTENDO says this is the best time in games ever (I think I am blocked by him because I am too negative or some such nonsense). I just don't see it. If someone has a list of games that I am missing out that blow away everything that came before on I am truly all ears.