Asians are viewed as even less marketable than African-Americans. Aziz Ansari makes a joke in his new show where he says movie and TV studios are JUST NOW coming around to the idea that black people have money and are a viable audience demographic, but they don't even take Asians that seriously.
This plays into comics as well. There may not be any black a-listers, but Storm, Black Panther, Falcon, Luke Cage are probably more recognizable and prominent than just about any Asian superhero Marvel has published. They're only just now getting on the right track with Ms. Marvel and Amadeus Cho. For many years diversity just wasn't a priority for Marvel, and when it was, Asian characters were at the very bottom of everyone's lists.
Asians are very marketable.....if they are martial artists.
The bigger named Asian actors are foreign born martial artists like Jackie Chan, Jet Li and Donnie Yen. Most Asian American actors tend to move more towards TV anyways. Lucy Liu, Daniel Dae Kim, Masi Oka, Ian Anthony Dale, Grace Park, Ming Na Wen, Mindy Kaling, John Cho, Maggie Q, Kal Penn and Aziz Ansari. I think that if they want to cast Shang Chi, they'll go the foreign born Asian martial artist route. Colleen Wing will probably be an Asian American actress. I have my doubts that we'll ever see Wong in Dr. Strange or even an Asian American actor who plays an Avenger, unless they make Iron Fist an Asian.
As for Black actors in the MCU, each movie has added one well known name to it's cast. Each of them are fairly recognizable names: SLJ, Anthony Mackie, Idris Elba, Chiwetel Ejiofor, Don Cheadle, Blair Underwood and Chadwick Boseman (well, Boseman is not there yet but will be). They missed the boat on adding Will Smith to the MCU (as who though, I have no clue), but they could still add an even bigger African American name to it's roster of black actors if they go with my (longshot) suggestion of Denzel Washington as Norman Osborn. Not sure he would do it, but he would be awesome in the role. Plus they added Mike Colter as Luke Cage. Not sure where Forrest Whitaker would fit as I think the role of Robbie Robertson is too small for him. Same pretty much for Morgan Freeman. Not certain of superhero interest from the likes of Nate Parker and David Oyelowo. Also not certain if we want to see Jamie Foxx redeem himself in another Superhero movie after the disaster of ASM 2. Had he not been cast in the disastrous Fantastic Four, Michael B. Jordan would have been a great addition to the MCU. Not sure of Marvel's interest in John Boyega at this point, but he would certainly be on Marvel's radar if he becomes a household name after The Force Awakens (which I am sure he will be).
With regards to African American females in the MCU, there have been five so far and none of them are in the movies, except Zoe Saldana, but she's playing an Alien. Rosario Dawson, Alfrie Woodard, Christine Adams and Simone Missick are on TV. Something tells me that if they add Monica Rambeau, it will be in a movie and she will be a fairly well known actress or an up and comer on the rise. This is where I think Marvel runs into a major casting issue. Do they go with an actress who is closer in age to RDJ or Ruffalo or Rudd? If so, names such as Taraji P. Henson and Gabrielle Union should be on top of their list. Do they go younger, as in the ages of the three Chrises: Pratt (35 born in 1980), Evans (33) and Hemsworth (32). In that case, it's got to be Gugu Mbatha Raw, who is the same age as Hemsworth. Or is it somewhere in between like with Mackie, who is 37 or Cumberbatch, who is 39? In that case, it should be Kerry Washington (38) or Naomie Harris (39) or Paula Patton (39).
There are no Asian American actors who are box office draws and a lot the ones I mentioned have been gearing more towards comedic work on TV. Yes, John Cho is playing Sulu in the Star Trek movies, but he's best known as Harold in the Harold and Kumar movies and as one of the MILF guys in the American Pie movies. Hell, the most famous Vietnamese American actor is Maggie Q and she's only Half Vietnamese. As a result, a Vietnamese American like me has to look at Chinese and Japanese actors for people who are my race in Hollywood.
Right now, the best Asians can hope for in the MCU are Daisy and Melinda May.