The social media fan reactions from the screenings that were released before the actual reviews were mixed, and those are usually universally positive. Even Ant Man 3 and Rise of Skywalker had mostly positive reviews from those.
Also, the box office tracking is dipping into Morbius territory and seems like it will open much lower than The Flash. I've seen conflicting reports, but The Marvels either cost 200 million or 250 million. This could be similar to Black Adam flopping for DC where they reassessed and scrapped their universe and started the reboot with James Gunn. And, in hindsight, Black Adam opening to 60 plus million with a superhero the general audience wasn't that interested in or aware of, is a testament to The Rock as a box office draw. Especially after all of the superhero films from this year besides GOTG 3 and Spider Verse flopped worse than Black Adam.