It’s funny because when you boil it down, that’s really only true of maybe two or three of the big supervillains

Magneto, who basically wants mutant Isreal and how correct he is to want that changes depending on the writer

Dr. Doom, who concocts most of his plans to cheese off Mr. Fantastic and is usually content with ruling Latveria

Count Nefaria, who is pretty much a c-list villain whose most famous act was killing Thunderhawk, another c-list character

Most other Marvel villains have plans that go beyond becoming a fascist dictator