So I'm trying to unlock the blue building. I'm on 236/250 so I only have 14 left to complete.

What I don't understand is how under "earning" there are quests like "complete day 6 of morostide 2018 plot" like... it's 2019? Is it still possible to do these plot quests, and if not, why are they in my list of "in progress" achievements?

Usually past event achievements are retired and only show up if you completed them. Maybe they just haven't gotten to the latest one yet?