Honestly, Gran Turismo 7 really lacks a bunch of modern super cars, hyper cars and a bunch of various categories of race cars and etc.
But that isn't the point. Gran Turismo was and always all about those Japanese cars, adding as many as possible and obscure as possible, which is why I think we all love Gran Turismo as a whole. It's main identity of the game you could say.
If GT7 would come out initially with updated GT500 cars, let's say from 2021 as well as perhaps add some oddballs from GT300 cars, using mother-chassis, like Toyota MC86, Toyota Prius and etc. Everyone would rejoice in happiness, because Gran Turismo is all about that—it would feel much more complete.
This gaming franchise has never been mainstream, compare to let's say forza horizon which has a ton of cars that only few can afford or those modern GT3 cars that everyone wants.
So genuiely, if anyone wants those newer cars such as Ferrari 296 GT3 or Porsche 963...perhaps they'll eventually come, but it'll take some time.
People want those cars, because PD is literally the best there is in terms of car modeling and such, which is quite understandable.
But as I said, the game is not mainstream, it's Kaz's own child...albeit still in 'beta' state (incomplete career, rabid chase ai and etc)
GT7 certainly has a good carlist in terms of Japanese cars, but not those that speak to you 'it's late game now! You've come so far...'
Perhaps I'm just getting nostalgic over GT1/GT2 games, where you would go from a literal Prius to a Legendary JGTC cars, but that's just the spirit of Gran Turismo. (Of course in future installments we would go further into F1 90's cars, LMPs and RedBull Xs territory, but they all feel like an 'addition' in my opinion.)