OK, I wasn't going to say a high quality lens is important, but I can see where it might come in handy.
I use a 135mm Xenar 4x5 enlarging lens you might say has a certain amount of "character" and I've been fine with it. I know it isn't APO type N or anything like that.
But lately I have been unhappy that my enlargements don't match my contact prints. I can't stand it and my solution to the problem is that I'm not going to make any more contact prints.