Dr. Strange and the Multiverse of Madness is not very good. The main problem is the script which is just a litany of set pieces and action sequences without a clear purpose. In good script writing something happens because something else happened because something else happened. In bad script writing something happens and then something else happens and then something else happens. DSMOM is bad script writing.
The second problem is that what little valid causality there is comes from exposition. At the moments when the writers realized they needed some explanation for what they wanted to do next, they just gave a character a speech. Exposition kills.
The third problem is that the dialogue is flat and dull and all attempts at humorous interjections fail. It's hard to say why this is. Cumberbatch, McAdams, Wong, etc. all are capable of delivering a comic line. It could be that these moments were poorly timed in the darker tone of the film. It could be that they just picked bad takes during editing. Whatever the case it didn't work.
The fourth problem is that it is heavily, heavily contrived. Eg.
The MacGuffin in this case is a teenager who can traverse the multiverse. How and why she can do this, we don't know. She's not given much of a personality. The only personailty she is given is identitarian -- she is Hispanic, with lesbian parents -- so it seems she is only served up as a diversity symbol.
There are cameos that are huge for Marvel fanbois -- Patrick Stewart, John Krasinski, etc. playing iconic characters -- cute, but purely a gimmick from what I can tell.
The characters' powers are both enormous and vague, which allows them to do anything that the script requires whether it is coherent or not. I cannot emphasize enough how much this undermines any superhero movie. It's also lazy. This has become a huge problem at Marvel. (I could write an entire post on this one.)
The final battle is an ode to Evil Dead (thanks to director Sam Raimi, I suppose), with combatants throwing musical notes at each other and zombie joint snapping and so forth. It is absurd to the point of cynicism.
In the end, you're left with nothing but a sense of pointlessness. No harm will come to you from watching it but set your expectations properly. It is a timepassing curiosity at best, unlikely to be rewatched. Don't pay money for it beyond any streaming fees you're already paying.
The final post-credit scene is Bruce Campbell crying in relief "It's over!" It makes me wonder if the film's creators knew it wasn't very good.
