Yall both made good points. I would say a few things tho,
(1) Nobody (i'm generalizing) liked Thor's faithful adaptation (through two solo movies and two Avenger movies) until the tail end of the Infinity saga when they allowed Hemsworth to ham it up with the humor in the YT skits and then Ragnorak.
(2) Also, while they kept Steve Rogers a relatively faithful adaptation, it wasn't until they landed an emotional cord with audiences with his relationship with Bucky in TWS and juxtaposed Steve with other MCU characters in his movies (Widow, Falcon, Fury... then Tony, Peter, T'Challa), that he took off. Nobody cared about him after First Avenger.
(3) Guardians of the Galaxy... yea lol. Threw adaptation to the bushes and made a bigger hit than any x-men (sans DP) or F4 movie.
My point is, neckbeards don't represent general audiences and catering to them (faithful adaptations) was not why the MCU was successful. It was well-written emotional storytelling
ignited by the "innovative" execution and success of Avengers 1 (aka the "payoff" for watching all the other shyt leading up to it).
shyt storytelling killed the MCU brand, point blank. "Faithfulness" itself was bushed before the MCU even peaked, and let's not act like a lot of faithful comic stories aren't dog shyt anyway