The Psi Corps successfully created a being as powerful as a Vorlon in Jason Ironheart. While the research staff who successfully did it was killed, it should not be too difficult to re-create what was successfully created before. If it has been done before, it should not be difficult to do it again. If it has been done before, it means the present state of technology is not too far off.
Why didn't Psi Corps do it again, given that success would mean the human race would make a huge leap in technological power that can help them beat the Minbari and match even the Vorlons and Shadows?