I did a final viewing of my edit, and only now realize the similarities between The Shadow and Doctor Strange.
- Our hero starts as a talented but selfish, insensitive person,
- He finds a hard road to redemption in a remote place in Asia,
- From a bald-headed Asian mentor teaching him mystical abilities which he must use for good.
- The villain in the movie is a fellow/former disciple of said mentor, who mastered the mystical abilities before betraying the mentor.
- The hero fights the villain in the hall of mirrors / mirror dimension (different names but visually remarkably similar).
Stan Lee and Steve Ditko grew up with radio and pulps, so it's understandable they were inspired by The Shadow. Still, their Ancient One does seem a lazy copy of the Tulku.
The mirror dimension did not exist in the comics, it was first introduced in the 2016 movie, 22 years after The Shadow movie. Louis D'Esposito worked on both movies. It's visually very reminiscent! Yes, I know The Shadow's mirror room was inspired by Orson Welles' The Lady From Shanghai (1947). But the visuals in Strange are much closer to Shadow than to Shanghai.