I wouldn't call the reviews of BR2049 and Dune mixed. Both films have about 90% on RT and 4.1/5 on letterboxd. That's far above average. Every movie has at least some okay-ish or bad reviews, that's normal. But Dune is obviously considered generally favourable.
Not coming into the discussion of "good" or "bad" but time will position those films in the right place... We might get a surprise in some years from now.
Who might think when Flash Gordon was realized that it might become a cult movie (again not saying that it is a good movie... but yes a cult movie, independently of my opinion)? Maybe Flash Gordon next ToC?