Actually, in
Brawl, airdodging after being launched
canceled your hitstun; it didn't cancel your momentum directly, but it allowed you to do something else that would. This made hitstun in
Brawl effectively cap at 13 frames (the minimum amount of time before you could airdodge out of hitstun (the minimum time before you can use an aerial out of hitstun is 25 frames)), which is why
Brawl is considered so combo-unfriendly. Hitstun canceling was dramatically weakened for
Smash 4 (with the minimum frame threshold for being allowed to do so being dependent on things like knockback velocity); I’m not sure if hitstun canceling is a thing in
Ultimate or how strong or weak it is if it exists, but in any case, the limitations on airdodging in
Ultimate (as opposed to being able to repeatedly airdodge in
Brawl and
Smash 4) means that airdodging to (try to) hitstun cancel just hinders your ability to actually dodge things.