My guess is that the vast majority of T-rated games are just mediocre. They're too violent (thus can't be recommended for their innocent fun) to be E rated, but not mature enough (thus, usually can't be recommended for a deep engaging story) to be M rated.
Most T-rated games are just another entry in a franchise that has been going on for far longer than it should have - like pretty much all the latest Need for Speed games, and the FIFA games to some extend. Sure they're well selling games, but they're hardly a compelling title to play.
That's not to say all T-rated games are bad or boring, its just that the vast majority of them these days are. Back in the PS2 days, Jak and Daxter was one of the best T-rated games I played. I don't think there's anything remotely close these days.