We share the same opinion exactly. I completely agree with your point about the books. I've read every book, comic, etc and that game still made no sense.

I also agree about the gameplay. Warzone was probably some of the most fun I've had in a Halo. I never got good enough for regular slayer ranked though so I can't comment there.

4 is my second favorite campaign for story, but I am a book fan so I may be biased.

Infinite lacking the set pieces is what really killed it for me. Where's boarding a scarab? Where's giving the covenant back their bomb? Where's tank beats everything? Where's the death star trench run while the best song ever blasts in your ears and the Earth hangs over you to show you what happens if you fail? Where's jumping down an unfolding Guardian?

The open world is why we couldn't have those set pieces in Infinite because approaching from any angle makes them basically impossible to choreograph well.