I thought this thread might have been about the ability of older people to have LDs, not whether people in the past could do it.

I suspect the only thing that has really changed is global communication. Now more people know about LD because of this site, Inception etc. etc.
Before I'm sure a few people stumbled into LDs naturally, and many will have had vivid dreams but just not known there was another level.
Even today, if you ask people, a large number don't know about LDs, young or old.