@anandxxxIt's all stuff in the game's fighting engine.
I won't crazy into it, but I will rant a little bit here.
Basically, when I first got into Street Fighter IV a year or so ago, I was still new to it, wasn't playing online, just learning the basics. But once I got SSFIV and soon after, got live... I started wanting to get better. And at first, I felt like I could without spending 24 hours a day on the game and attending every tourney. But as of the past couple months, I feel like I'm banging my head against the wall, and even getting worse at the game.
The biggest problem, is link combos, the most annoying thing in the game to do: basically, to get certain oft-used combos to work, you have to press buttons at a very specific frame. This is hard enough to do offline/local, but online? It is the most frustrating combo I've ever had to do. People can say what they want about Tekken's combo system or Tatsunoko/MvC's long combo strings, but at least I know if I do the commands properly, the combo normally hits. With Link combos, it feels like there's this... 90% chance it won't hit unless you spend months JUST practicing that combo.
The next problem comes more on an individual basis: some moves online are extremely hard to punish, no matter how often yo u can do so offline. Ken's weak Dragon Punch might as well have no recovery time, and people will ALLWAYS follow it with another one or a strong one or an Ultra. It's... agitating.
Third thing? Speaking of Dragon Punches, I'm tired of 90% of the online users playing as Ryu. Even with over a thousand matches in, I feel like I don't know how to fight half the cast because all I ever run into are Ryu, Guile, Ken, and Akuma. Dudley and Balrog are really high in use too. But Ryu... oh man, if I never fight Ryu again, it'll be too fucking soon.
There's more, but these things by far have really weakened my like for the game. And I still like the game, I do (just played it today for as long as I could stand). But I cannot wait until I get KOF 2002 UM (which I know I like more anyhow), and Blazblue CS (which many of my local friends have switched to).
Aside from that? I'm reducing my fighting game time and getting in some more MHT time.