The campaign has some decent missions, specifically the Meridian chapter, but for the most part it tends to be forgettable, with either too many or too few enemies placed in spaces which don't feel tailored to them. There's also a reliance on glorified GIF skybox 'setpieces' which feel like tedious gimmicks rather than the big event that battling the Scarabs in Halo 3 and engaging the Corvette in Halo Reach were - this sort of thing was acceptable in 2004 with Halo 2's Scarab, it isn't acceptable in a $250m+ 2015 game.

The Prometheans are certainly better than they were in Halo 4, but they're not great to fight. Sometimes it feels as though Knights and Watchers lose track of you while literally standing in front of them, other times Soldiers teleport so much that neither you nor they can hit a shot. Vehicles are underused and when they do appear, it's very limited and underwhelming. The Covenant are better than the downgraded units from Halo 4 also, but they never quite reached the AI heights of Halo Reach and had an extremely limited weapon sandbox.

Graphically, the game leaves a lot to be desired though. Face models in cutscenes are incredibly impressive, but the flat lighting and plastic-like materials make the entire game feel like toy soldiers in a bad way.

Overall though, I agree with you that it's fun. Definitely one of the weakest entries in the entire franchise, but very playable and much less of a snooze fest than its predecessor. I felt Halo 5 had some extremely promising core gameplay, outside of the bizarre way they implemented sprint (you're punished for using it, but it's required to traverse the map effectively and tied to three core mechanics), but it really suffered from samey weapons and a lack of good, developer-made levels and maps to really showcase that gameplay. Community map playlists almost felt like a different (and much better) game.