If Covenant 2 never gets off the ground, it's for the better. It's time to move away from the prequels. I've said before that the prequels feel like nobody (including Scott) had any idea where this was all leading to. I mean no insult to anyone involved in the making of the films, but with Covenant specifically, I think we were dealing with the making of a movie just for the sake of making a movie. Don't get me wrong, David has been interesting, but he was never trilogy level interesting. The one thing I think Covenant accidentally managed to pull off was a suitable ending. Having secured his freedom and accomplished his goal of creating the perfect organism, we are free to leave David and his story behind.
When you don't have to worry about adding new species and whole civilizations, you can focus on writing good characters. This is the crux of any film. The characters on screen are the individuals we (as an audience) live the experience through. We follow them, we root for them, we fear for them. They are the most integral part of any film. I love Alien, it is my favorite film in history. But, had it not been for the characters and the solid way they were written and handled, even that film would've suffered for it. Character development and implementation is key, without it, you can have all the cgi and explosions and hoopla in the world, and still have no decent film to speak of. This, I think, has been the greatest failure of the prequels.