Legalism just means someone who keeps the law.God doesn't want that from His people rather He desires relationship. I think sometimes we categorize those who strictly adhere to an outward standard/rule as a legalist but really anyone can fall into the trap of trying to win His favor through human efforts. Even a good ol' Baptist may think that if they pray enough they can make it to heaven. A Catholic may think that reciting a ritualistic prayer and lighting candles may earn heaven or at least purgatory.
Conservatives think that long sleeves and abstaining from "I Love Lucy" make us holy enough. We are often very serious about the Lord and therefore choose to live a separate life, unfortunately if we fail to remember that our efforts are but filthy rags then we are no better than the Pharisees. Our standards have to be a fruit of the heart, adhered to because we love Him and others. A bowed heart will indeed bear precious fruit, problem is many are trying to hang good lookin' fruit on dead dried up trees.
He is enough.
Luke 11:42 But woe unto you, Pharisees! for ye tithe mint and rue and all manner of herbs, and pass over judgment and the love of God: these ought ye to have done, and not to leave the other undone.