Well, it's not an important point but I suspect that our greater knowledge of nuclear forces eases the engineering challenges. The neutron was discovered in 1932 and I don't think we can meaningfully talk about nuclear physics before that date. So that puts the field at age 10 in 1942. It is now 90+ years old. I think that counts as infancy, but more importantly it doesn't matter.
The point is, as you say, that the physics is not terribly complicated, and the engineering problems have mostly been solved. It's just a question of running the centrifuges.