Is it time to Sunset FFXIV?

[Sotaris]

A lot of the 2.0 code is based on 1.0 since they both share the same engine, sort of.
1.0 used the infamous Luminous engine and 2.0 uses a altered 2.0 version of it, shares a lot with it.
Wherever they replaced it without communicating it, I can't say. I don't work at SE. I suspect they still use components from it, other parts is replaced since they was able to do some form of graphical overhaul this expansion.

That they can't change things due to 2.0 code is proof to me, someone who been working as a developer for the past decade that they rushed, took an old codebase to get 2.0 out on the market as soon as possible instead of doing it right from the start. We see it at most companies so SE isn't unique in this. It was just a matter of time before their legacy spaghetti to bite them.

I'd call that technical debt, since they can't do massive changes without having to rewrite a lot of the legacy, even if Yoshida don't think it is. Might just be a difference of labels.