That's really not as easy as you're making it sound. I'd like you to any game that is completely fixed with absolutely no issues. I'll wait.
And yet, that still has flaws within it's own system that results in a hit or miss experience. Not perfect, but getting to a point, much like most any game is trying to do. With the high focus on Multiplayer, balanced racing, and strict homologation, you'd expect a game like GTS to focus on that first, rather than Forza. It's the actual core of the game, and it makes sense for GTS. I think they should be implemented into Forza as well, but lets not pretend they're focusing on the same things.