As I see it, believing in aliens is incompatible with being a Christian. Christ died for humans, the only creatures made in His image (with a rational soul). All of creation , apart from its purpose of glorifying God, is in a sense , made for us. The “there must be aliens because the probability that we are the only planet wirh life blah blah “ position has the underlying assumption that the universe is random and made from pure chance. But this is wrong , since it was created. And literally created for us. Not for aliens. Humans are the stewards of Gods creation and the beneficiaries of the blood of Christ. To entertain the idea of aliens is to diminish Creation and Gods redeeming work in our Lord.
Good video explaining why aliens are condemned (not explicitly but he argues it is the correct interpretation) in the Catholic catechism