Just as a note, I'm playing it on the master chief collection, and it's disappointing that they ruined the textures by losing the code. Unfortunately, that makes the game look much worse than it actually did even in 2001. Also the lighting is pretty atrocious so I had to switch back to remastered graphics a lot during dark sections, which was pretty much the whole back half of the game.
Gameplay wise though, this is a fun game even in the current day. Enough old school jankyness that it adds some flavor, but competent enough shooting mechanics for it to feel polished. Piloting a warthog has be purely nostalgia based though because those things are the devil.
All in all it's a solid game made even more fun with friends in co-op, and I'm looking forward to going through the rest of the story, as it feels like it's only really starting to ramp up in terms of lore building.