Nothing wrong with the writing of Halo 5, the point with Halo 5 was it was chopped up into 3 different parts. A trilogy which means that Halo 5 had to lead up to what's next. The story has already been written awhile ago and if you have finished Halo 5 on Legendary you will be excited with Halo 6. There's much more to come in the Halo Universe. Even though Halo 5 didn't live up to expectations from the adds, it still has one of the better stories for a FPS game.
My problem with the ending in particular is that it does not satisfy me it sort off ends with a "In the next episode of the walking dead" without satisfying me or concluding something relevant to the story arc,in Halo 4 Master chief mission was returning to civilization for better or for worse he completed that mission in Halo 2 while having a similar ending problem to this one it completed the whole Arbiter story and the covies civil war. I dont get that in Halo 5 its just like a massive episode one of something with the majority of its content being filler aka Locke segments.