A Combination of Factors
Whitewashing, Deviations From Source Material Annoying The Core Fanbase, and it being ****.
But its slightly different no anime or manga adaptation is going to make it in the west if the Western Fanbase is ******* on it nonstop.
Now New Mutants.....its riding on good will to the actresses currently cast that is the only thing it has going for it.
Its already deviating heavily from the source material which usually doesn't go over well.
The whitewashing debate over Sunspot isn't likely to help.