I don't think you'd argue that an incompetently made movie is a work of art

You are making a fundamental mistake: that art is venerable by nature. I.e., if it is not venerable, it is not art.

I would insist that an incompetently made movie is a work of art, actually. It's very interesting to me that you wouldn't.

then that opens the door to saying that art by Hitler, [...] are important.

Fascist art is actually very interesting because there is a perverse artlessness to it.

The nazis were not good artists. They liked big, masculine, square stone blocks. They liked big nipple domes that communicated power through their sheer size and their size alone. They hated degenerate, jewish ornamentation and artistic flavor.

Their depiction in recent Wolfenstein games is notably cool as shit, but also entirely unlike them: the gothic-esque qualities of those pillars and tall buildings would have been seen as degenerate, damaging the masculine austerity they wanted to project.

Their art, their marble statues of strong, muscly soldiers, venerates status and power in a purely aesthetic, unthinking kind of way—you're not meant to think about it.

Now, why point this out. You keep bringing Hitler up in an obvious attempt to disgust, as if the words "Hitler" and "important" in the same sentence are itself a crime, but "important" doesn't have to mean "good." It doesn't even have to mean "likeable."

Hitler is a very notable historical figure, I'm sure you can imagine why, and his art, and the art of his fascist contemporaries, is an important reflection of what they were like as people: boring and stupid.

Why should I care if Ringo Starr or Jim Carrey are "important" or not? They don't deserve to be? Does "importance" come with a trophy or something?