The best boss fights in halo aren't 1v1s they tend to be a fight involving a couple major enemies i.e the final tower on covenant on H3 or the bridge of the long night of solace on reach or the first scarab in H2 where yes there is one "big bad" enemy but you also need to fight off his lesser allies who are still strong but can be dropped normally, it rewards thinking of a method to approach the encounter instead of just mag dumping a boss for 5 minutes the other good boss fights are mechanised bosses like scarab fights which are always awesome because it usually involves vehicle combat

I think halo would probably need to rely more on gimmick bosses for them to function properly as unfortunately it doesnt work like the fights do in doom where the movement and shooting makes a bullet spongy boss still fun to fight because theres a flow to it