BvS was not panned because it wasn't Marvel enough. Wonder Woman, Aquaman and Shazam weren't exactly like Marvel movies either and they turned a profit and were not panned. Notably, they are all getting solo sequels which Snyder's Superman is not getting. Neither were darker movies like the Nolan Bat films, Joker, Logan or Deadpool and they all did well. it was panned for having a bloated, joyless story, an annoying antagonist and one of the leads being an uncharismatic piece of wood and ill defined/unlikable characters in general, which are all credible reasons to discredit a movie that features well known children's characters that rely on new generations of kids/families to keep them afloat. Even releasing an extended cut wouldn't have helped, as it would only have helped a few plot holes but still have all the problems the theatrical cut had, just an added 30 minutes to an already 2.5 hour slog.
The Marvel movies are mainstream blockbusters and aren't super deep to the point where people are mostly entertained by them and move on. But beyond the fanboys, the general audience doesn't spare much thought to BvS either. They don't dwell on it much either way, it came, it sucked, and they moved on to the next thing. Online discussions by fanboys (in the positive or negative camps) are not indicative of anything. Neither set of films sparks serious film discussions, because they are big budget studio driven IP farms designed to sell toys.