its all the same except for grenade/sprint and crouch it has been the same for the past 10 years so why change it
It really hasn’t been the same since Halo CE. Halo 3 was much different from Halo 2 and reach with equipment. It’s changed throughout the years, I see no reason why it wouldn’t change again especially with the addition of sprint as a default.
Grenades have always been on LT (or top four buttons for that fact overall), but I guess after 12 years, we just needed to spice things up and confuse the Yoink! out of everyone and make them waste their 1 of 2 of their only nades unless they have a certain Specialization every time they insta-spawn… 
It started changing with H3.