What theme did they copy from Marvel? If you’re talking about multiverse stuff, that’s been a concept in comics for ages and DC introduced it into comics first. Marvel bringing it to the movie screen first doesn’t give them ownership of the idea.
You could literally prove yourself wrong by exercising just a little intellectual curiosity. Marxism is, at its core, an economic theory based on the idea that democracy has as much a place in the workplace and economy as it does in our political system. If that’s fascist to you, you’re unserious.
Now, if you’re just unwilling to correct or criticize your own beliefs, and you want to conflate Marxism with Stalinism and Tankies, you’re better off just saying so.
If the political consultant is Mr. Pillow I’m going to die laughing.