This show wanted to be everything, and failed at all fronts. This show wanted to be a mecha anime, wanted to be cute, wanted to be """"""""political"""""""", wanted to be SoL, wanted to introduce some mythical """"""""lore"""""""". Unfortunately, it failed at all of these (except for being cute, thanks QP-Flapper).
The premise seems to be good in paper. Unfortunately, the execution is terrible, the plot development is terrible, the script is terrible and the characters are underdeveloped. Aside from Yui, Rena, and Ingrid, I barely knew any of the other characters, and they barely made an impact on the show. The worst offender of which are Tia and Sara, which have no personality beyond some assembly of tropes whatsoever. At points during the final confrontation with the villain, the protagonists are spewing cringe-worthy shit, whatever the villain is saying stopped making sense and the I stopped caring about the whole thing.
Since the name of this show is "Regalia: The Three Sacred Stars", I'm going to give this show a 3 stars out of 10.