Nobody's telling you to stop wanting thief. Nobody is telling you to stop asking for thief. Hell, I WANT to play as Thief. That's pretty much my main go to in EVERY single Final Fantasy(including XI) and other RPG I play where it's an option. In FFXIV I will be playing as Rogue(and to go along with your perspective) I will be "maining" Ninja, because that's what is available(I also have a hard-on for Ninja, but that's besides the point).
What I AM saying is that demanding something blindly without really looking at the facts(of which there really are none at this moment) or respecting/trusting the devs to do something interesting and/or fun with an old idea is unfair. I'd say the same thing in the countless RDM or _insert job here_ threads.
Also a protip: Based on what you say about not appreciating the Duty Finder, I take it you're a fan of building a healthy, helpful, and friendly community. Antagonizing fellow forum posters with bullish tones won't do anything to help that.