It's time constraints. A typical 20 minutes (minus the OP and ED) of a standard length episode is some 14,400 frames at the typical anime 12 fps.

That two minute video was done from October to April, and it is absolutely loaded with shortcuts. Anime studios have far less time for ten times the length.

Take a look at the OP/EDs of tons of recent anime. That's where you get all the ambition. It's 1:30 (that can get reused), has to serve as an advertisement to the series, and they get to spend more time working on it because it is either done in advance, or slapped on when they finally finish it after some lazy stand in sequence.