The entire online experience has been, for me. It's hard to get into quality rooms and find games, the difficulty of making money and everything being absurdly expensive, glitches, and my god, the loading times. The loading times are by far the biggest deterrent to play for me so far.
I also can't stand how many races there are compared to everything else. It's not a racing game, and I don't want to race, ever. I want to do heists, infiltrate places, assasinate, etc. Leave me alone, I'm not playing Forza.