Real competitive fighting game players don't use online. No matter what fighting game it is, it will have enough lag online to be unplayable to any person who plays competitively. Even Virtua Fighter 5 for Xbox 360 suffers from too much button lag to be playable for competitive tournaments using its online.
Franchises like Super Smash Bros and Mario Kart have two fanbases... the competitive fans and the casual fans. However, the competitive fans tend to ruin it for the casual fans once online is involved. Just look at Mario Kart DS. It was made much like previous Mario Karts, and the competitive fans loved to snake, and thus ruined it for the casuals.
You seriously don't think that if Brawl had Wavedashing, that there WOULDN'T be complaints about online play? There would be topics about how Wavedashing ruined online because everyone is doing it. If you cater to the fanboys, you lose most of your casual fanbase, while the fanboys will almost always complain that you didn't do it right. What Nintendo has figured out is that you should cater to the casual fanbase because the fanboys will buy your game anyway. That's in fact the whole point of the Wii.
I want everyone who has played Brawl and hated it to think about this... If Super Smash Bros. 4 actually was annouced right now, are you willing to wait to hear about SSB4 before shelling out money for it? A fan should be willing to stop being a fan if they start hating the work. I myself am a fan of Sonic the Hedgehog, but I've stopped buying console games after Sonic Heroes, because I am not a fan of messy glitchfests. However, I do still like the fact that Sonic is in Brawl, though not because I've ever really wanted a Mario vs. Sonic showdown. I owned both a Sega Genesis and a Super Nintendo during the 16-bit era, and liked both Mario and Sonic. No, I actually like the fact that he is the Sonic I remember.