Different Animation Techinques

Even during the first episode you can see shots you could call "pencil drawings". Those were made clearly on purpose and worked effectively.

Episode 19 that is the clear oddball with those stick cut-outs as Rei mentioned earlier is at the end of the day some weird experimentation they had the balls to make (due to budget constrains, yes, most likely).

Recaps episodes (14, half of 15 and 24) is what is really concerning in a sense, and those are easy to skip. 19 and 25 are "simply" weird episodes (disappointing if you expect the same pace of plot progression as in the beginning of the series though), and 20-24,26 introduce character arcs that won't see completion in the anime.

The main problem of this series is ironically starting very well. When it stops being as good it does so in such an obvious fashion it's almost impossible not to be left disappointed.

But as far as the visual efforts seen throughout its episodes, well. I can barely compare it with anything else. I find it commendable overall.