I don't believe in anything supernatural, but mysticism doesn't count.
Supernatural means beyond nature. No such thing. If it's part of the world, then it is natural.
But parts of the world are still mysterious. Unlikely coincidences shatter our notions of causality. Modern physics struggles to provide a coherent definition of "time", other than "it's what a clock measures." Consciousness is a deep, dark well in which science has only dipped its first toe.
Mysticism accepts and celebrates the mysterious. Sadly, some folks have mystery-blindness.
When little kids grow up with severe colorblindness, they think that "red" and "green" are invented concepts, non-physical – like how "hot" and "cool" get used to describe desirable things.
It can be a great shock to these kids when they find out red and green have physical existence. That other people can perceive something they can't.
Some people think current science describes everything in the world. They usually go even further, that anything not described by current science doesn't exist.
I'm sure these folks have never had a spiritual experience, and for that I feel sorry. But I have to see it as hilarious when they announce that no one has had a spiritual experience, spirituality doesn't exist, that your feelings are incorrect.
Science defines the external world that we all share, and it does that magnificently. But our internal worlds require a different type of investigation.