Obviously, Graphics can always be better as many here have stated. That said, Generation leaps are much smaller now than they were in the past. Seeing footage of Xbox Series X gameplay for example. It looks amazing, but it really isn't that much more impressive than the Xbox One X. If you compare the PS1 to the PS2, THAT was a full generation leap. But from what we've seen from next generation, it's looking like we'll just be going from low settings to high settings. Better, but not earth shatteringly superior.
Oh man that is a good way to put it. That pretty much hits it on the head. Take a current gen game and raise the settings and you get a next gen game.
Even the leap from last gen to this gen, while more noticeable and perhaps a bit more than just "low settings to high settings" isn't so great that now you look back at PS3 games and think they look bad compared to PS4 games. They still look great just a bit less so. It's not like going from the pixelated glitchy jagged mess that was PS1 to the vastly improved PS2, or PS2 to HD PS3. Those were large leaps, though obviously less so for the latter transition but the jump to HD made it feel bigger. PS3 to PS4 was a bit less than PS2 to PS3 but also you didn't even get the huge resolution upgrade so it wasn't that big a difference. Without the jump from HD to 4k I think the next gen leap would be entirely unimpressive as far as generational leaps go, and even with it, as you say, it just seems like going from low settings to high settings, or even medium settings to high settings!
The generational leaps since 3D have basically been "very basic 3D" to "good 3D" to "really good HD" to "great HD" to next gen "slightly more great 4k". The 3D generation leaps have gone from huge to big to decent to now next gen "turn the settings up."
Now I get why loading times are like such a big deal in next gen systems, because other than the jump to 4k (which Pro and X owners already experienced) the graphical upgrade isn't that big so something like load times becomes a major differentiating factor in the generations. Ray tracing seems to be like THE BIG DEAL for the next gen. Watching videos of ray tracing it IS really cool looking, but again, in terms of upgrading how games can be made and played it doesn't really do anything, it's just a "oh that looks cool" feature and considering that seems to be the major upgrade people are excited about it is underwhelming for a whole generational leap. Reminds me more of the intra-generational leaps during the SNES like getting the FX chip or Rare digging into the system to be able to produce DKC graphics.
At this point its gonna be a full decade before there is even any graphical reason for the next-next-gen to come out. Makes me think Nintendo is ahead of the curve here with the Switch because after the next gen it would seem to me that the only real way to show tech progress would be to miniaturize it with slightly better tech after a decade into a hybrid form so people can play whenever and wherever. As graphical power has already stopped making much of a difference between generations, Nintendo's current strategy of play anywhere I think is the next logical step for the advancement of gaming.
And since for years to come next gen games will likely also be released on current gen systems, but with high settings turned down to medium settings it feels like there is less reason to buy a next gen system at this point, not saying people won't because most people like the to get "the new thing", but just saying there won't be much difference between playing current gen games and next gen games.