Is it me getting old or has the industry stagnated?

Horizon Zero Dawn is a must-play Action-adventure.

Metro Exodus
https://store.steampowered.com/app/412020/Metro_Exodus/

Ori and the Will of the Wisps
https://store.steampowered.com/app/1057090/Ori_and_the_Will_of_the_Wisps/

Resident Evil 2
https://store.steampowered.com/app/883710/Resident_Evil_2/

Control
https://store.steampowered.com/app/870780/Control_Ultimate_Edition/

99% of the industry just trend-chases because their hiring practices prioritiezed certain check-marks over actual talent and skills. This also led to way too much bloat, much like we've seen in the rest of the tech industry.

annual Assassins' Creed

Sorry, did you seriously just list that as an example of NOT stagnant? I beat Assassins' Creed 2, "the best one," before 4 was released, and even back then, I thought the game was extremely dull. For the parkour segments, you just hold forward and the A button, and you'll make every jump successfully. For the combat, you just tap the X button, and you'll win every battle--even against the final boss. The game stagnates within itself, and it doesn't take long to do so. The only bit of variety was when you have to use a smoke bomb to steal something from a guy in a crowd without being noticed, and that five-second-segment was the only time you had to use any item ever.

Go back and replay some of those games you listed--or at least emulate some of the popular games in their genres that came before them--and you'll see the AAA game industry has been this stagnant far longer than you've realized. It's not that you're too old now, but that you were too young then.

I've actually probably played more in the last few years (2016+), and I've tried lots of games.
I've noticed the more I play, the less games (and (sub)genres) I actually like.
A lot of the big genres people like, I hate. The big genres that seem to pump out lots of clones.
I'm quite content working on my backlog so much, that the age of release of a game really doesn't factor in.
Yep, I still play recent games, but AAA games are only as good as the indie games they try to keep up with.

Both. The industry have certainly fall into formulas and AAA studios are avoiding all risks and trying to tick all boxes of the biggest sellers in the past, leading to samey stuff, rushed stuff etc... and despite the huge amounts of money made the biggest blame is on mobile gaming.
Given how we live in a capitalist status quo, where all big companies work under open capital, the majority of decisions stay on the shoulders of investors- the same ones that jump ship as soon as stock value decreases....
...and in that world justifying a multi-million 3+ years behemoth project that may still bomb, while in the mobile world a half-assed cash grab made in 6months-1year and profit the same or more... it created a crysis

So the big companies fight said crysis in multiple ways- from cuting corners, to cutting risks, to rushing, over working their devs... So its samey stuff that releases with bugs, cut content, anti-consumer practices, etc, etc

Go indie.

THAT SAID...
THE BIGGEST CAUSE IS YOU(US)- AGE.
And im pretty sure on that. Real life have its toll, and it fits right in with what many said of 'been there done that'.
Novelty is certainly a huge factor, and the novelty factor only dimmishes with time.
...but... id say not only that either. I mean, its harder to find but fresh novelty can still be found- and ive still seen me and others my age or older not getting as hyped up/moved by true novelty.

My counclusion is a bit of the opposite...
...its the youth.
The youth that is overly impressionable, overly hypeapable. Not only have they experimented less so everything is fresh and newer, it have something to do with stage of development or less burden (from life)- everything (besides gaming) can and do feel MORE the younger we are.
More everything- more new, more magical... but also bigger and more important, both the good things and the bad ones.
A breakup? Is bigger. World issues are bigger. Bad comments or offenses from peers are bigger.

Everything is larger, everything takes a lot more space in ones mind both in scale, time and significance the younger they are, and this span to ALL things.
For example i havent seen that only with games. From parties to books(ive always been a bookworm) - i mean, BOOKS for gods sake, where theres no gaming crisis or 'triple A', where its impossible to have read everything good or unique that existed prior... if no new books were released a single human couldnt read in his lifetime all the great, unique books acumulated so far, and being unique they would all be fresh, be it from this century or centuries past...
...and i feel the same dimmishment in return too

I hope that dont let anyone down... the same sort of feeling from the past can be achieved, by varying degrees, and heck doesn even need to feel that novel- its more of a 'everything clicked so well for me, right now' effect- that at least for me is unpredictable. I cant tell if a game, film, book or what have you will click specially with me and spark peak joy. Now its trial and error, happenstance

One BIG tip to improve your chances: GO OUT OF YOUR COMFORT ZONES.
In terms of gaming, start trying/playing some games of genres you never tried, heck even some you hated.
Of course many will stay hit you the wrong way- but theres far, far more chances of finding that novelty and renewed interest there because of the uncharted waters left in a niche

Oh, and (im very biased saying this but) try tabletop rpgs if you havent. Seeing you like rpgs... its the only thing from my youth that, even if it lost some small bit of its novelty, it never stoped being wonderfull. Besides the huge amounts of variety and novelty in the genre, each campaing being a different story, different gms and such things can be never dull. I say it have 5 layers or variables that prevent that- ruleset, setting, story-premise, gm and player- if someone played games for years in the same setup and starts feeling dull changing just 1 of the variables make everything fresh again. If you get into groups on different games/gms each time... EVERYTHING feels novel and different, all the freaking time- and the stories can go better and more involved then any AAA game

There is stagnation amongst AAA publishers because they are too focused on trying to make the game that will generate them ALL the money, but with so many failures recently I think we might be nearing the end of the live service era. But if you aren't ignoring the rest of the industry then no, you're just getting old.

I think it's the same problem with movies. Copy and paste is very safe and rarely fails. Starting a brand new IP is risky.

Dunno, found some rather unique gameplay-wise in these of the last years at least, don't think there are many "alike" them at least.

Hardspace shipbreaker
Talos Principle
Satisfactory (and factorio)
Ultimate Admiral Dreadnoughts
Kingdom Come deliverance
Slay the spire (-> this set roguelike deckbuilders back in the spotlight 4y ago)

I'm just glad a lot of console ports finally make it to pc, like monster hunter series and so on

The AAA game IS stagnated. But you can still find really good AAA games like others have mentioned.
Indie games however are lots of fun, if you're willing to explore you can do it yourself.

That being said, there's one title that you must absolutely need to check. And it's an indie title: Disco Elysium.

One of the reasons in my opinion is that there's been more "evolution" when It comes to online games where communication is key. I still feel the online multiplayer changed the way games can be perceived and there's still alot to exploit there.

For example G.T.F.O. takes the level of sound you make "in game" to create an atmosphere but the time will come where the A.I. will react to the level of decibels you create and to the stress of your voice when It comes to online co-op. And that will be dope.