This is a series that is creatively stuck in the past.
We've had two prequel films, one film that's stuck between two classics and now a TV show ,that's coming our way next year, that's going to be yet another prequel.
Surely there's interesting stories to be told after A:R ?
They don't need to be straight up sequels either.
Just on the basic premise of Alien Romulus (scavenger kids in space) alone sounds like it could have brought the series into the future, especially if you're going to go down the route regarding the after effects of The Auriga crash, a ship that had its own myths and rumours from the outside and now it has emphatically crashed itself into a bleak, dystopian earth. From outside there's alot questions there about why this came to be.
Maybe the kids in Romulus stumbled upon the famous xeno once again when traversing through space, when all speculation of the beast died out and just became mere myths or rumours.
Creatively I think you have more breathing space (boom,boom) to go from there than to make a film that's wedged between two others, personally speaking.
Chronologically this is a weird franchise. People just want to go further and further back.