It's so early on in a fighting game's life that people don't know what's balanced and what's not. All of those complaints may seem bogus to those of us who've been playing this non stop, but not a lot of people have been able to see the qualities of these other characters. Sweet Tooth's level 1 super isn't something to laugh at. He can get it quite quickly if someone uses him well. Thougb, the fact that it can be negated easily helps even that out. Sackboy's moves had to be nerfed but his meter really is pretty large to fill now. Though I have noticed those with skill that use him play pretty well and can gain meter pretty quickly (though, in my opinion, he can be a cheap character, depending how he's used).
All of these complaints are sound. Don't mock them simply because you're good at the game. Not everyone can "master" a fighting game so quickly. At the same time, there are already answers to these complaints. Instead of unintelligibly mocking them, show them why some things should be fixed and others not, instead of being one of those jerks I find in every other online match.