My experience with MCU is that you have Marvel Cinematic Universe fans who often roll in one or more subfandoms and do it all in the umbrella and you have TV show fans who do more than one show usually but treat them as their own fandoms, with the possible exception of the Netflix shows.

I've always been an umbrella MCU fan and prefer to be able to offer from there, especially if it includes characters from the TV shows I know. I prefer merged fandoms for those who treat it like one canon. I've always liked and preferred the individual TV shows available to those who just want to request/offer those but don't do any requesting/offering in those myself.