Yep. The real problem here is his performance and inability to get better (he's oblivious to the fact that he's bad).
Which is kinda in part is Asuna's fault too, she doesn't tell him how to improve, maybe change things, try something else out. Her first and only solution is to cheat lol.
Kirito doesn't seem to be bad at sex, and he seems to have a chance of being normal or even good, Sinon and Suguha like it, and they've had more experienced partners.