I think people may have heightened expectations when maybe they should be tempered.
If this were GT, it would be filled with comments about how difficult it was to make 700 cars and 30 tracks for a 4k game.
How they had to remodel old models, update textures and resolution.
It looks like they spent good effort and time bringing back disappearing models, which seems to have been widely requested.
Obviously rebuilding previous models takes time away from making new ones.
I think they're doing fantastic. Sure, there's cars I wish were in the game, tracks too.
At the end of the day, you can only compare it to it's competition, which it no longer really has. (It looks like pc2 is closest, but that's a much more dedicated racing simulater with a vast array of racing machines and effectively, a very different game)
Even if it's all disappointing, it's so far above and beyond it doesn't really matter.
It is so much the new Gran Turismo it's not even funny.