What is the wealth of fortresses of players who have problems with no visitors? Because I don't have this problem. In fact, I find the visitors annoying, because they enter no matter what other life forms are present on the map, sieges, beasts, whatever. I have a fortress in its 4th year, had dozens of visitors, and no less than 20 present at any time. Created wealth is listed as over 4 millions (most of it roasts), and I think it is a magnet for visitors. I have no barkeep, no scholars, only one scribe (probably doesn't matter anyway) but they keep coming.
I have checked 20 random visitors with WorldViewer, using my world in legend mode, from before the fortress was created (I keep the save for things like that). All of them were historical figures, and they were active before my fortress was established. Many of scholars and poets created artefacts and written contents and forms before. One ranger-bard created 16 such forms. Human dancer, part of a troupe, created 35 written contents, and one dance form. The queen consort, who is currently visiting my library, created in the past at least eight artefacts, plus some forms, and discovered knowledge (autopsy). Some guys are just active, no discoveries and creations as such. They are coming from other civs, even dwarven. So I suppose they must be chosen from among hist figs, not created out of thin air.
However, to test it truly, it would need a world near its end, with dead civs and not many historical figures to choose from.