Short answer: no.

Long answer: Ratings for these kinds of films are... well, they depend on the source material. And the majority of Marvel comics are written for all ages. Deadpool works because what you're giving the rating for (violence/crude jokes) is what that character is famous for. It is an intrinsic part of his character. As such, to do that character justice, a higher rating is best. Very few Marvel characters need a higher rating to make their films 'good' or true to character. The character development is what is important and you don't need a 15/R rating to do that for most Marvel characters. The only other Marvel character that I think would need a higher rating to do them justice is The Punisher, because that character's is based around violence as well. Most of the time, a film isn't long enough to have both the elevated levels of violence AND the character development needed to make it a sound choice UNLESS the character is a naturally violent one. The reason the higher rating works for Marvel's Netflix titles is because they are longer. I don't think, if Jessica Jones or Daredevil were made into feature films (disregarding Ben Affleck Daredevil here) they would need to be 15/R films to get the point across. They aren't naturally 15/R rated characters. You can have the character development without the explicit violence. It would make those films different animals to the Netflix shows, but then again, film is different to TV, so that's understandable.

Like, you'd be hard pressed to do a Sex Criminals film on a 12A/PG13 rating, because the story revolves around sex. But a Black Widow or Hawkeye film could (imo) easily be done on a 12A/PG13 rating. Plus, you don't need a high rating to make things violent/unsettling/etc. I haven't seen it but apparently Batman vs Superman is very violent for a 12A/PG13 film. And the Studio Ghibli film Grave of the Fireflies is rated 12/PG and when my friend told me to watch it she said "If I would make all the world leaders watch one film it would be this one and there would be no more war. I think I cried more at this film than when my mum died."

Upping the rating doesn't automatically make it a better film. It works for Deadpool because of who Deadpool is. That doesn't necessarily mean it would work for their other characters. Plus, you know, Marvel have done eleven films on the 12A/PG13 rating. It would be a pretty big shift in tone if they changed now, and if Disney bought Marvel Studios for the young boy fanbase, they're not going to change it now.

This.

Yep, nodding along to all of this. And the thoughts about the difference between ratings for films vs tv shows considering their length, that's interesting and makes sense to me.