Steve Rogers once had the ability to turn into a werewolf, that didn't factor into the movies either. Its not simply a matter of "what is happening recently", its a matter of "What is core and logical for the premise of the character?" Lots of 'recent' arcs for various MCU characters were also very obviously useless for the movies, because they were either badly written or only made sense in light of a specific momentary plot need within the comics.
I don't think it's the same, captain America literally being able to have the ability to turn into werewolf. Just takes away from the uniqueness he has from the super solider serum. Plus his movies already established what he was capable of, from cap 1-3 they focused on his speed, strength and skill which work.
Shang chi being able to create clones doesn't take away from his martial arts, or him being a Master of marital arts. If done right it can actually potentially add to him, being a master of kung fu.
He can even use his clones as a form of training, maybe he takes on 3 version of himself which could be interesting, that's shang chi going against himself, but not one not two but three duplicate version that are almost the same as him.
I remember when captain marvel was first announced and there was an argument made, for why she should have her binary powers and why she shouldn't have her binary powers.
Also the Mohawk helmet, I remember there were a number of people who did not want it in live action movie. Because they thought it wouldn't translate well, same for her binary powers, and the same argument was made that her binary powers are more of a recent Developments, In comparison to when she was first created.
Now here we are and they adapted the helmet, and her binary powers.
You can have shang chi be an amazing fighter, and still able to clone himself without taking away the stakes, and we don't have enough information to go on. To suggest that shang chi being able to clone himself will take away from the story.
It's simple. Despite being based on,
shang chi is not Bruce Lee.
chi has to be unique as a character, yes the filmmakers can pay homage to Lee, but it's clear they also want to avoid outdated racist stereotypes.
So far everyone I've met who did not know that shang chi can clone himself. Were excited to a degree but once hearing that he can make clones of himself, is one a new power set in the mcu.
And two His clone powers to go along side his fighting style to help, Shang chi fighting style stand out. But hey that's me if they give him clone powers I am in, if they don't I am still in.