I'm a fan of the marvel movies but was let down by this. It first of all felt a bit cheesy at the start and I wondered why a girl is being chased by a big Mike from monsters Inc. But it seemed light hearted enough, then bang! Next thing I know I'm watching a cheesy marvel themed horror that was unnecessarily gory. Creepy and not in keeping with the movies which is something I feel you have to factor in if you're going to have characters cross from one story to the next.
And why bring in fantastic 4 and xmen when those worlds have not merged in previous movies. It feels disjointed.
Make Wanda a villian by all means, but after what she's experienced would she commit mass genocide across multiple universes? Seems out of character for her.