Honestly i think this game gets a bad rap. I never played the multiplayer so this is just about the campaign. The campaign gameplay is not as good as halo 3 or reach, but its on par with halo 2 and better than halo 1 (mostly, there are some exceptional halo 1 levels like silent cartographer but there are tons of repeated . The actual level design is pretty good. The armor abilities are well tailored to the levels and overall its a solid fps campaign.

The main problem is the promethean levels, and the main problem with them is not the watchers but the weapons. All the promethean weapons suck shit to put it lightly which makes the levels they appear in feel bad to play. They are all pretty much worse versions of other weapons. That makes the prometheans feel worse to fight. Only the boltshot is unique and even it is not great. The lightrifle is the only one that feels reliable, the scattershot is a worse shotgun and the SMG (forgot the name) is absolutely terrible.

But the watchers are fine and kinda like them. They are basically the same kind of enemy as elites or halo 2 brutes. You take down their shields then headshot. They have less visual feedback but they are pretty much the same. The little flying drones are actually pretty cool and remind me of the huragok from reach with their utility.

Spartan ops is clearly kind of an afterthought and i dont take it into consideration when judging the game. The other games dont have something like it so i dont feel spartan ops being kinda mediocre is really that much of a negative.