"Well, a good game maker software (which c2 poorly tries to be) should have a decent image/sprite editor (with functional at least similar to paint.net)"
C2 devellopement isn't over yet, so I guess it could improve some day
"well, too bad. Just because html5 won't stay for a long time, but EXE games are forever (steam, anyone?)"
HTML5 won't stay for a long time? EXE games forever? that just doesn't make sense, I can tell you even all exe games can not work well in the future (Hexplore won't work at all on 7 and XP, I think there is a patch for XP, but I never find it), but HTML5 is multiplatform, so I think if browsers still support it (I think they will let it be supported even when it'll be obsolete, but not sure), this can be valuable.
well-done HTML5 is slower than well-done exe? well yes, but not all games need that.
HTML5 only for web apps? no, just no, it can handle more than that.
I think your issue with C2 is that it does HTML5 games, you are not the only one with this, people tend to think C2 just serves the purpose of webapps and small games because of HTML5, but in reality, it is more like tring to let serious games accross all platforms, even the ones that are not obvious for that.
Also directX requires you to install the corresponding version, and even drivers sometimes, but drivers problems mostly handicap the C2 's editor rather than the game.