Sorry that I did not quote your full post, but I would like to comment only on these two paragraphs.
It is absolutely no challenge to get the 1000 cars challenge, because you can get it absolutly easy by buying 1000 go cards, get the challenge and resell them. That's it, it's about a days work and it is one legitimite way to get this challenge, which was intended by PD, because otherwise the challenge would require 1000 different cars.
The second paragraph is my favourite of your post. Did it not come to your mind that people are exactly doing that by glitching? Who wants to drive the same car 20 times because PD chose to insert 20 times the same miata/eunos or whatever the car is called, same goes with the skylines, and half a dozen more of them.
People want to drive the cars which they enjoy. Some of those cars need quite a lot of credits. And why spend the time in which they could have fun driving the car with grinding? This is the most important question to ask. Why should they spend time they could enjoy with a boring process which is not necessary? So they glitch to have more time to have fun and experience the cars they want to not the cars which are just affordable for them.
This is just like in real life, if there would be a way that you could get any car you like, you would take that way, as long as it has no negative consequences for you. You wouldn't drive a Golf or Prius if you could drive a Bentley, Mercedes, Dodge or something which is more fun to you, or would you?