He might not be interested in the horror elements of the creature, but he is very interested in the world and the "Why?" behind the creature's existence and how it relates to the lineage of creators and creations that he is exploring.
I think to say that Ridley isn't interested in making Alien movies is disingenuous. To say that he isn't interested in the Alien itself is, too. He just has his own set of ideas for how he wants to explore the baked in concepts of the franchise and I, personally, as both a fan of the Alien films and a fan of Ridley Scott as a filmmaker and his ideas in general, want to see his narrative here concluded.
After that, bring in another filmmaker to do what they want with the Alien. Knowing Disney, you'll get something much more traditional and close to the first two films then. That's inevitable. In the meantime, let Ridley finish up what he's doing and have his fun with his corner of the material here.
Personally I feel Ridley has a massively skewed idea of how interesting the creation of the alien species is to people. Outside of fan's of the franchise keen enough to sign up for a forum ie us lol, probably very few are intersted. Most probably went to see the prequels because they thought they were seeing a Alien movie.
We could have had Ridley making a proper Alien sequel instead we have this indulgence. It's all a missed opportunity to me. If Ridley wanted to make a movie which didn't feature the alien he could have made Beverly Hills Cop 4, or anything he liked.
If it has to be a personal indulgence on what Ridley wants then sure make the third pre-quel so this tedium can be finished for good and we can get on to what people really want to see, a full blown Alien sequel baby.
