It does seem unlikely that GT5 will ever get matchmaking, now that the online services have been turned off.
As far as GT6, the big miss so far has been the monthly track DLC, announced back at the Silverstone GT6 reveal. There's been some little stuff like the reveal and subsequent disappearance of Zahara.
There's also the "technically true, but seriously come on now" stuff like 1200 cars. Nobody is fooled. They have a lot of cars, more than any other game. But there are not 1200 unique ones any more than I can make one car, duplicate it 1199 times, give it 1200 different names and say I have a game with 1200 cars.
All the bollocks they went into about their new and fancy tyre model, the one that didn't actually take camber into account until it was patched in six months after release.
The ongoing dishonesty of advertising a game using premium cars, when only a minor proportion of the cars are of that visual quality.
There's also a reasonable amount of doubt that they can actually fulfill the requirements of the VGT program. There are 4 (?) cars released, with a couple more expected soon. They have 28 total manufacturers, to be delivered over the course of a year. They have five months remaining, and 24 cars remaining. Who here thinks they can suddenly step it up to releasing five new cars every month until December? Possible, but at no point in GT5 or GT6 history have they released cars at anything like that rate.
So they've missed a couple of big ones, there's still a lot of big stuff we're waiting for with no real information about, and there's a culture of "little white lies" in the advertising, not telling the customer the real truth about how the game is. It's used car salesman tactics, and it's sad to see from a company that produces what could be a first class product.