I think it deserved to do better at the box office but I disagree calling it that good, primarily by counterexample (which I’ll get to). It had an entertaining cast, an entertaining plot and some good twists but it wasn’t unpredictable and the audience it was best for was the audience who recognised the constant homages to the experience of playing DnD - my primary example is the scene of the main character breaking out of prison completely unnecessarily.
The movie was made by Hasbro to sell dungeons and dragons (which, to be fair, you do mention) and I think as a fan of the ttrpg it did a great job of capturing that experience as a movie. I can’t call it the film of the year though, let alone the decade.
What makes you say it’s better than, for example, Blade Runner 2049 or Avengers Endgame, both being movies similarly sprouting from established brands? I would argue Dune is significantly better (talking about movies with a brand) also.
Outside the established brand space, you see movies like JoJo Rabbit, Marriage Story and Power of the Dog. All of my examples have been off arbitrary top 10/top 50 lists of the last 5 or last 10 years and I’m honestly curious about why you think the DnD movie beats all of them?
Edit: in saying that, upvoting because this is almost certainly an unpopular opinion