While in an ideal world, they would go back and fix ARR to make it more interesting, I don't think you realize how much of an undertaking that would be. That would basically require them to rewrite and remake ARR so that it's more narratively interesting but still covers all of ARR's beats (even though ARR didn't have a strong through plot like the expansions, it still does a lot of leg work. It sets up basically everything to come in HW on).

And that would cost a lot of resources for something that most of their current playerbase won't even touch since they've already done ARR and would rather just get new stuff. And if recent reports are anything to go by, newbies aren't much of an issue right now either. The game is doing fine population wise.

In a perfect world where Squeenix had infinite resources and infinitie staff, an ARR overhaul woukd be cool. But as things stand, from a business standpoint they'd be crazy to spend time and energy on it. ARR is the worst part of XIV, but as things stand, it's good enough.