[drigel]

Yes, I think it comes down to a matter of understanding. What do Men do when they don't understand something?

So, Rivendell was at least a place that Men could understand and knew about.

I always looked at that somewhat the same, but a little different. Rivendell was the home of Elrond Half Elven. More ties and more responsibilities with mortals. But I always thought that Rivendell, as the third age drew on, had less official contact with Gondor, leading to none at all. So, as far as I read it:
Rivendell - friendly (Last Homely House, etc), run by an Elf Loremaster, but a hidden location (in general terms, especially by the later 3rd age).
Lorien - not hidden, but avoided. Im sure men of Gondor and Rohan (and other inhabitants) knew exactly where the physical location of Lorien was. A golden forest would be hard to miss. But, it was an alien (mallorn) place, and an elvish kingdom ruled by a Queen\sorceress etc. Travellers would turn away as soon as they saw it on the horizon (throwing salt over their should as the did). Plus from a Rohirric POV, Lorien was on the other side of Fangorn, another ancient wood, not enchanted but just as dangerous and avoided.

I think we can question whether Galadriel was the greatest save for Feanor

Yup. But I always reconcile that quote (and it's contradictions) in UT by interpreting that as meaning the greatest Noldo still living by the 3rd age (but isnt Elrond in that category as well? At least technically?). Traditionally, I would think that there were a few Noldor buried and under the sea considered greater. But perhaps, if she was the greatest save for Feanor, it may be possible that her role in ME was such that it wasnt demonstrated so readily, or obviously. She was as ambitious, but mabye not as mission driven, so her deeds werent as documented in song.