The thing with surviving X, is that you can't just be smart or strong enough to fight well.
Surviving X is a sort of balancing act, and being too strong is actually detrimental to survival against X.
Basically, 2011x takes your soul and puts it into one of a few select vessels of Sonic characters based off of your personality, these vessels are actually much weaker compared to the actual characters, being slightly stronger and faster than normal humans. For bossfights characters, that's actually a pretty big nerf. X has complete control over your existence at this point, and you can only really play along and try to not be "boring" to X, otherwise he'll just erase your soul.