I understand your concern. You are probably a person who likes to challenge others online and/or for local play to prepare yourself to compete in tournaments. For these purposes, some may say that Vanilla has satisfied. However, you may need to understand that not everyone who plays MvC3 care to compete. There are some that would want to find more ways of playing their game.
I live here in Los Angeles and have had access to several fighting game venues, such as Wednesday Night Fights, ReveLAtions and Evo in Las Vegas and have made efforts to participate in each one. When MvC3 games are played, they do generate a lot of hype at both the venue and on online streams. I get that, but the people at the venue and on streams are just a speck, a small percentage of the gaming audience. Others who pick up MvC3 will look at the menus and ask themselves, “Is this it?” and feel disappointed. It happened with my niece and her siblings. It also happened with members of my office when I first brought the game there.
When it comes to people who are not at the competitive level, variety keeps them playing. The more they play, the more likely they will get better. As they get better, they’ll start finding challengers. The more challengers they fight, the more confidence they will have in the game. People who have confidence in the game will more likely want to join or even establish their local fighting game scenes, which is good for us in the FGC.
It’s okay that you do not like my suggested modes, but you must admit that MvC3’s offline and online offerings are lacking. If you have mode suggestions, speak on them.