Halo had some unique enemies. Or unique types of aliens. They aren’t like other aliens from other games and movies you know like making them into a rabid super powered creature or incredibly high tech impossible-to-kill machine.
Instead, they each had special ways to fight and lore reasons on why they fight in such manner in-game. But in Halo 4-5 they kind of lost that feeling besides the basic points. Now, grunts are all the same no matter who carries what. Jackels don’t matter what shield it is and they tend to not be able to be killed with hand to head tactic in Halo 5, and everyone as an Elite can carry an energy sword or turn invisible to command troops.
It is little detail complaints but it made it look organized. The only way they would be like that with good reason would be because the covenant has follow and their rules on who does what falls also. But this is gameplay we are talking about. Not theorized lore.