It's a very average movie.
Nothing new here, apart from the owl-bear I suppose. Owl-bear !? Some of the cast were personable but they had very little to work with. Otherwise unimaginative and forgettable.
I saw it at the cinema, and the only reason why was because tickets were sold out for the Mario movie. Otherwise, I don't think I would have ever gone out of my way to see Dungeons and Dragons. Since I know nothing about the franchise.
I thought the movie was....fine. But like you said, very forgettable for the most part. As I was leaving the theater, I heard two guys (who had been sitting next to me during the movie) talking about it, and they were like...."Meh, the movie was OK". They sounded disappointed, lol. Also, for such a lighthearted movie that never takes itself too seriously, that horror flashback felt very out of place. I'm talking about the one that shows Xenk as a child running from monsters during the spell.