Well that's sounds like an attitude I won't miss.
Why do people always feel the need to rip on a past game claiming that "Game X" is bigger, badder, and all around an improvement? Sure, GT has it's downfalls with development and communication from PD, but the core game itself is great. There's a ton of veriety in it, and I don't play it as much, but I still enjoy it every once is awhile.
My honest opinion, Forza really doesn't offer all that much more, aside from a few different cars, and tracks. It's the same concept, same general game, in a sense.
Compairing Forza 6 to GT6 is like compairing apples to oranges anyways. We're talking last gen hardware being pushed to it's limits nearly ten years after it's development, and Forza, or any other next-gen game hasn't even begun to scratch the surface of the tech that's in those consoles.
Now, some people just wish to upgrade to something different, but people that have to bash on GT when the upgrade just to get a final laugh in really aren't saying all that much. That being said, don't let the door hit you on the way out. Just sayin'.