The overwhelming majority of mutants in the X-Men universe don't have cool powers.
Many of their mutations are small enough to be concealable so they can pass for human with a bit of work, or they can be handwaved as having some slight disfiguration. Then there are the mutants who's mutations are too obvious to hide and who end up as societal outcasts, like the Morlocks.
Most mutants with functional powers don't attempt to join super teams either, because they're mostly just normal people caught in inconvenient situations. If they're lucky and somewhat socially mobile, they can attempt to move to mutant friendly communities, that are often one step up from the ghetto in terms of property values, but are somewhat safer for people trying to live free from the anti-mutant bigotry.
These stories inevitably resolve in tragedy as they find themselves being forced to take a side in some violent conflict and lose their innocence if not their lives, or they have their sympathies being mistaken and get unfairly arrested, or they become victims of anti-mutant terrorism, or they become a casualty of an anti-mutant genocide campaign courtesy the Friends of Humanity, the Purifiers, the Right, or Cassandra Nova.