...so, I am a bit disappointed as well, but this is business. It makes sense to also use the PS4 community to increase sales.
My take would be something like the following scenario - release GT7 cross-gen with bare minimum specs, then at some point release a 'dynamic weather, feature X' PS5-only patch. This way, they also milk PS4 owners - who will be happy to get something and also keep PS5 users happy because they get something exclusive to their systems.
But let's keep what can be done better in the PS5 without ruining the experience. Ray tracing, better distance LOD (for me this is currently a major put-off), better shadows, increased resolution (native 4k), better anti-aliasing, increased frame rates, use higher res 3d models as well. For me personally, GT Sport is good enough, and its graphics is certainly not what's killing the game (more on this)..
The fact that dynamic weather/time of day was not implemented in PS4, could be bad optimization - as developers work over time can solve any problem. I am certain they can squeeze more detail on the tracks as well, or make 3d trees (actually what they've done with the trees works really well in GTS). Also it's bad to compare to 'other titles that do it', because, we are talking apples and oranges.
...so, what would make this game better, is better AI and proper racing, not just 'challenges'... rushing to pass the first car; this fact alone means that there's huge rubber-banding, so the whole 'car class' thing fails. AI also uses computational power, but I guess this is not why they haven't messed with it, but rather because people learned to expect it from GT titles, and/or needs a lot of refactoring to make it work properly.