I personally own 4 games that max it out.
You keep pointing out maxwell cards, but maxwell cards are not as capable as a 1080ti.
Its hard to explain but what I mean is this, for many many generations the most powerful gpu in that generation was never powerful enough at least without SLI.
Pascal was the first generation where a single card was powerful enough to play games at max resolution at 60fps.
Maxwell was never powerful enough to do this, even on launch day. Same with all previous generations.
I expect if a 1080ti is good enough now for your needs, it will remain that way until we see next gen consoles at the very least, which is predicted in 2020.
Nvidia know this as well, so they had to create a tech for consumer space which "slows cards down", hence RT. Because otherwise people would stay on pascal with it been "good enough", the exceptions been those who always want the latest GPU.
4 games? That not very good enough to maxed out on 1080 Ti.
I checked both techpowerup, gamegpu and other sites to find lots of 2018 and old games which 1080 Ti are struggled to maxed out at 4K a year after launch that the same thing happened to Maxwell, Kepler, Tesla 2.0, Tesla 1.0 even since back to 3dfx day when I found my old Voodoo card struggled with heavy demanded games and upgraded to Banshee. It really not very hard to explain, it is called GPU bottleneck.
Here are some 2018 games benchmark reviews list below 1080 Ti cant hit above 4K 60 fps with graphics settings maxed out:
Assassin's Creed Odyssey
Call of Duty: Black Ops 4
Darksiders III
Dragon Quest XI
Dying Light Bad Blood
Far Cry 3
Far Cry 5
Final Fantasy XV
Fortnite
Generation Zero
Ghost of a Tale
Hitman 2
Hunt Showdown
Jurassic World Evolution
Just Cause 4
Kingdom Come Deliverance
Monster Hunter World
No Man's Sky Next
PlayerUnknown’s Battlegrounds
Shadow of the Tomb Raider
Shadows: Awakening
State of Decay 2
Total War Saga: Thrones of Britannia
Total War WARHAMMER II
Vampyr
War Thunder
Warhammer Vermintide 2
Yakuza 0
Some of above games 1080 Ti only hit 4K 30 fps as well as my old GTX 1070 struggled to hit 1440p 60 fps maxed out in Just Cause 4, Far Cry 3 and other games.
If people really want a GPU that will not bottleneck in games between now and in 2019 at 4K above 60 fps, you will have to buy either RTX 2080 Ti or RTX Titan which these 2 cards will be very powerful enough to drive 8K games at above 30 fps with DLSS so your 1080 Ti will not handle 8K games at playable fps with maxed out graphics settings.