What you're actually insisting an IP owner and creator do, is give you their IP for free..
Not at all. I've already bought and paid for that IP when I bought a copy of the game.
What are you talking about? You bought a license to use a game developed and wholly owned (including any in-house IP) by the company who created the damn thing. You, don't own any part of that beyond a compiled installer on read-only media unless the company happens to be publicly listed. And then you're likely restricted to a certain class of shares that essentially translate into you having NO real power beyond an investor willing to lose everything.
I would expect that licensing agreements for IP holders, while time limited, cannot be retroactively applied. If the car models and likenesses are already on the disc, it is impossible to remove them. I can see there being a stipulation that no further instances are to be sold or made available once that agreement has expired (which would be a reason to stop selling the game, for instance), but customers who already have the game already have those models/likenesses in-hand, so allowing them to continue using them is not in violation of any agreement.
If there is merely a contractual agreement between the game vendor and the car vendor, which both vendors agreed to licensing of that car vendor IP for a fixed period of time, then the expiration of that license is STILL between the same two vendors. Likely the reason Ubisoft is jettisoning any official support for the game rather than offer any type of alternative, is because Ubisoft was contractually obligated to do exactly that upon IP expiration. Is that a shitty tactic to force vendors to extend IP licensing with or-else type verbiage? Sure. Am I shocked if that was the case here? Not in the least.
Neither of the parties or contracts involved related to that IP, involve you the consumer in any way. You have been given a EULA-limited license to the game. With likely zero inherent guarantees regarding network play. And I doubt you're going to find even EU law in support of the consumer after 10+ years of support.
You the consumer can keep the game and continue to play (locally) with the skins that are already on the disc because you didn't sign the IP agreement with a car vendor now putting on the squeeze. The ones taking down all official support did.