Interesting. I was disappointed with Halo 5's campaign enough that I didn't really give matchmaking/forge a go.
But from what I've seen online its forge is really impressive, and it's amazing that some of the things made were done on an xbox.
Campaign did feel like it lacked stuff, but the multiplayer is pretty good, overall, it's a step up from Halo 4, but i still prefer Halo 3 and Halo Reach
But Halo 5's forge mode is definitely the best one yet, but being used to Halo 3, Reach, and 4's forge, Halo 5's feels really complex and overwhelming since you can actually script stuff, create terrain, add weather effects, decals, change textures the textures of basic forge pieces and how shiny or dull their textures are, it's a lot to learn and get re-used to
I'd say Halo 5 is at least worth getting for the multiplayer and forge mode