Based on the first chapter's TN, wouldn't the title be better translated as "powerless saint and talentless princess"?
Yes, but on the cover of JPN raw ch01 the author decided to add their own English version of the title in small scripts, so the translators just kept that. Some similar cases I could recall off the top of my head are Whispering You a Love Song (Sasayaku you ni Koi o Utau), Demon Lord of "Yashiro" (Yashiro no Maou), I Want to Make Black-Knight Fall In Love With Me! (Gakeppuchi Reijou wa Kurokishi-sama wo Horesasetai!),... Usually such small script titles are not the most literal translation, nor are they oftentimes the best translation, unfortunately.