I was disappointed by Alien Covenant too. Action scenes are ok but the story and characters are poorly written. You don't care about a single one of them when the aliens are not on screen, and the first 30 mins was dull as hell apart from one action scene. Fassbender was the best thing in it as usual but even he had one horrifically awful scene (recorder nimrod?).
I also watched Arrival last night. Really good sci-fi story which was let down by a disappointing ending and a plot device which shat all over the previous 1hr 45mins. Same director who is doing Blade Runner (Villeneuve) and who did Enemy (which I thought was $#@!). He can do sci-fi obviously, but it's gonna need to be well written.