I haven't seen Covenant, but Prometheus was a disappointment. I somehow think they betrayed the wonderfully mysterious invention of Giger - the peaceful star gazing victim of the Alien merged into his machine - by making it a large white human. An imaginative regression.
We have to go back in time and force Ridley Scott to make some more SCi-fi masterworks instead of this sad decline!
I agree on everything you wrote above. The Stargazer was a great concept from Giger, and much more powerful while it was open to any interpretation. By explaining it (and in a bad way!) all the mystery and fantasy was gone.
As for Covenant it was a good stand-alone sci-fi flick, but it does not fit into the Alien "mythos" as we enjoyed it with the original films. A pity. There are some great scenes with the AI-android pondering life, creation and eternity. Still, I like Ridley Scott's films; just yesterday I enjoyed All the money in the world.
I also like his films, but the first ones are really artworks! While writing I decided to find this Covenant and watch it.