It lacked all the magic that made Halo so great, Boring encounters, I hated the bullet sponge prometheans enemies and they were not fun to fight at all. The whole ship sequence was dreadful, The AI was not up to par and It lacked the epic battles that halo is known for. I didn't bother with MP as I play Halo for the campaign only.
Then I think you'll like Halo 5.
There is a ton of open areas that lead to large scale multi-plane firefights and plenty of really fun vehicular combat in midst of the big firefights. To be honest this was my favorite part of the campaign, I truly thought the combat was really fun.
The environments are really vibrant and I found myself sometimes just looking around at the areas cause they looked so good.
Skulls and Intel are really well hidden which encourages exploration of the areas and there some cool bonus stuff to find.
No bullet sponges except for maybe some of the hunters with their shields but I didn't really find it annoying or anything like that. All the Prometheans have a weak spot that makes taking them down pretty easy.
All that being said I didn't really enjoy the story as much as I have for the previous games. While I didn't have an issue with Fire team Osiris, I just felt it was off that they would introduce Blue team (4 spartan II's who grew up together) and you barely hear them say anything.
The Campaign is designed to be played Co-op and I think it would be much more enjoyable with real teammates rather than not so good AI.