3. The Script Is Basically A Mess
Few are going to argue with the ambition of this new batch of Alien movies: Prometheus posed some extremely tantalising questions about the creation of both the humans and the xenomorphs, and though Covenant has its share of fascinating moments, the script is also pretty much a mess.
The sometimes laughably on-the-nose dialogue (such as when David tells Walter "I'll do the fingering" while teaching him to play the flute) and tendency to ask more questions than it answers while mostly disregarding a number of Prometheus' more interesting plot strands is sure to leave fans frequently frustrated.
Again, the sheer scope and mythology-expanding nature of the film helps it overcome a lot of the more indelicate creative decisions, but you'll probably be left craving a more coherent and considered end product, especially if you're a hardcore fan of the earlier movies.