Never send a Brit to do an American's job.
I guess they figured since it worked (kind of) with Christian Bale? But at least Batman had a reason to disguise his voice; his hoarseness had purpose. Here it just sounds perpetually like Strange needs to cough something up.
Other problems included the weak attempts at defining character (that music thing, I guess?), the unconvincing arc of Strange's asshole-to-hero story, and Cumberbatch's utter inability to sell a joke. Which became a joke in and of itself, but hanging a lampshade on it does not excuse it.
The plot, meanwhile, had all the usual earmarks. A "regular guy" (by which we mean, of course, a rich jerk, in this case a neurosurgeon) goes through a terrible ordeal (car crash caused by his own assholery) and in the course of recovering discovers amazing abilities that allow him to transform into a superhero. His mentor (the much decried Tilda Swinton) turns out to have a fatal flaw and of course dies and leaves the hero to take on the heavy burden of continuing the goal/quest/whatever.
Oh, and the goal/quest/whatever in this case is to fight someone the mentor trained who then defected, and beyond that to fight the "dark side" or something, and then to continue the job of defending against that dark magic or . . . something . . . that we're never really made to care very much about.
They also shoehorned a romantic subplot into all this that was pointless and held no chemistry.
I suspect what they might ultimately have been going for was: "What if Sherlock—arrogant know-it-all that he is—gotten taken down a few notches and then became magical?" Why else get Cumberbatch, whose high note as an actor is: insufferable? Seriously, half the time Strange simply comes off as a facet of Sherlock anyway.
Also, Cape of Levitation? Really? No, I get that a lot of this comes from the comics, but when the CGI cape is funnier than you are, there are problems.
And just because you learned some magic, you did not suddenly learn martial arts. Those aren't the same thing. That's a different skill set.
There are some nice visual effects here, but they can't make up for the blandness of every other part of this movie. So. Pedantic. So. Rote. Just no charm to it at all.