My main issue with 30fps before was really high input lag but they've figured out ways to mitigate that a lot recently.
Horizon 2 has amazing input lag in the 30fps mode, 60fps feels better but it's not like night and day, meanwhile image quality takes a massive hit and is very noticeable on a large display at a viewing distance where you get the full benefit of 4K, which unfortunately is unreasonably close in a room used for things other than gaming. So for most people with families and/or more than average sized rooms you'll need a giant display.
If you don't have that kind of setup I can see why you'd think the IQ is meaningless and a waste of time when you lose half your motion clarity and some to a lot of responsiveness.
1080p with near perfect AA to remove all jaggies still look like 1080p, you lose so much of the detail of modern games even at 1440p imo. I just couldn't believe how much more detail I saw in Jedi Fallen Order at native 4K vs. 1440p, its the exact same with Horizon 2 its hard to appreciate the finer details in the performance mode.
I'd be fine with 1080p-1440p for games like Psychonauts 2 to get 60hz or even 120hz but high frequency detail demands higher res imo, otherwise might as well have the fidelity of the last gen since you can't see it through a lower res frame.
The exception for the above being lighting advances or other things that can still be resolved at lower 1080p.