Mind control magic is just one of many kinds of magic. There are other spells and countermeasures against it. Besides that, all mind control magic can either be resisted by enough willpower, or takes a long ritual to enact, that requires the victim to already be helpless.
Mind control is particularly feared and reviled. Fortunately, it’s never foolproof. On multiple occasions, mind control has nearly taken over the world, only for superheroes to step in and foil those plans.
For example, one current supervillain called Hypnodusa can control the minds of others by making eye contact with them. But, knowing this, heroes could deal with her just by never making eye contact. (The problem is that she’s in hiding most of the time.)