The "7th Umbral Era" storyline isn just a single quest chain. It's the combination of the main scenario, class and job quests, Grand Company quests, and primals. All of this is changing or going away when 2.0 goes live, so now's the time to do it all.

And you won't be "replaying the game from the beginning" in 2.0. Your character and his progress will be transferred.