Exclusive MCU fans are still Marvel fans, absolutely. They're just more niche in terms of their understanding because it's all Earth 199,999. They are Marvel fans, but just fans of an alternate universe. They are Earth-199999 fans.
What is a Marvelite?
Marvelite is a rare mineral created from the destruction of multiple Marvel worlds (TV shows, and different comic series). Marvelite seems to contain the essence of various heroes.
How many superhero cinematic universes are there?
Exploring the Four Superhero Cinematic Universes!
Are there two Marvel universes?
The Marvel Universe is part of a Multiverse, with various universes coexisting simultaneously, usually without affecting each other directly. At the beginning there was only one universe, The First Firmament, but due to actions of Celestials existing there, it diverged.
Are all Marvel movies in the same universe?
The MCU movies, however are all set in the same world (OK, Galaxy) and meant to be consistent with each other. We have two main groups of heroes - the Avengers and the Guardians. The most recent movie (Infinity War) joins them, and a few standalone characters together.