That's not surprising at all. I never trust Rotten Tomatoes and even less so when it comes to people spending their professional life critiquing movies suddenly being told to critique a movie aligned to a video game that hasn't even been released yet. I don't assume most critics are gamers.

The reviews from actual "normal" people who wanted to see the film have been very solid by comparison, 7.6/10 on IMDb, 80% on RT, 7.6 on Metacritic (3.5 for Metacritic's critic reviews). That's really good for a video game movie.

I always go by IMDb, personally.