No, it would be a good idea to get rid of a boring and annoying mechanic.
If people want to be cut off from content, that is fine. Not everyone does, and there isn't a single good reason to keep that content from them.
If you consider the mechanic of conventional video game unlockables a way of "cutting people off from the content" you may want to reconsider quitting gaming altogether.
For the record, I did get gold on all the license tests in games 1-3 as of now and my skills are mediocre at best, but that is beside the point because the truth is "not everyone has the same skill level" is in no way an excuse for instant/easy gratification in a game. As I said, any prize cars are only as unavailable to the player as the player themselves wants them to be. If, like me, you're willing to invest in the time to collect every single prize car in the game and get 100% completion, you do so, but not overnight. If you're someone who just wants to jump right into the game, choose one of the 700-800 cars that are, hypothetically, not prize-exclusive.
No thanks. I'll skip over the licence tests entirely because I've been playing GT games since 1998 so they have no learning value to me
First of all, I really hope for your own benefit that you're not trying to represent not only the larger GT fanbase, but the future players who have not yet experienced the series, with that statement. Secondly, that is a rather bold statement. While it is true that anyone can complete/gold the license tests provided they try hard enough I am highly dubious to the claim that you can gold any license test from the get-go or your skills are flawless.
It's actually kinda sad that someone wanting to play a game in their own way brings out disgust in you; which manifests in you insulting people again.
This is actually blatantly hypocritical. Let's say that Gran Turismo 6 had "only" 900-1000 cars as opposed to the planned 1000, the 200-300 missing cars in this scenario being vehicles that would otherwise be exclusive prizes. Would you, as a self-proclaimed strong black GT expert that don't need no career mode, feel cheated out of an experience? I highly doubt it; 900 cars is still a whole lot.
On the converse, imagine a Gran Turismo that has a terrible prize car system with no surprises, uniqueness or any excitement whatsoever...oh wait that already happened, and you can literally find pages of threads complaining about this particular mechanic; the GT5 forum is your oyster.
So which of us is really the one arguing for a mechanic that would enable them to play the game in their own way again?