It wasn't that bad, but you're broadly on the right track. The Ascians are the most extreme example of FFXIV's writing very rarely ending in the place it started, because the approach is usually to find the plot hooks to justify the story they want to tell. They were locked in on the Ascians being major villains, but they changed track on that story pretty hard; I don't think they had 'no idea who the Ascians were', but rather that the original plan of who they were got thrown out. I honestly very much doubt that the final idea only happened in Shadowbringers, though; it might be where they hit a generally solid state, but my personal estimation is that the 'present Ascians' first started coming into form in Heavensward's patches.
And anyone who thinks that's a negative, remember: every single Ascian fan loved them in Shadowbringers, most likely because of Shadowbringers, and we wouldn't have that without the devs' willingness to have and pursue better ideas.
So yeah, a number of these really old Ascian-related threads are just relics of a version of the Ascians that wasn't their final form. For the most part the developers are really good at repurposing those old pieces, to the point where the playerbase broadly sees those as 'unresolved mysteries' rather than parts of a rejected story (remember how long people banged on about 'what's under Silvertear Lake'), but with the Ascians having been a big part of the story even back in their early form, they just have a lot of bits lying around, and not all of them fit easily into the story we eventually got. After all, if the dark crystal was Zodiark, that would've been a really dull fight.
