I think that changes hit the Legion particularly hard because of the futuristic science part that's involved.
We're looking at exponential changes since the late 50's, after all.
If I were a scifi writer with a series of books in the 50s, 60s and even 70s, I'd let them rest as they are.
If I was trying to write a series now, I don't think I'd try to do an update of the same characters at their same ages or whatever is happening now.
I'd establish a fresh set of characters and settings.
But, that's just me.