That's not an art error.
This continent is indeed a regressed post-magitech-apocalypse one, with the Church of Grineer causing these contorted beliefs.
Summarizing least-spoilery part:
The human civilization on this continent are the survivors of collapsed human magitech civilization fleeing a post-war / runaway magitech-bioweapon overrun continent. Literally, survivors hiding in bunkers, fleeing on boats, abandoning the continent entirely. (Spoiler: said apocalypse caused by human stupidity, hubris, and greed.)
The church's orignal commandments were "DON'T MESS WITH KING-CLASS MAGIC CREATURES UNDER ANY CIRCUMSTANCES". And "El Magia is our creator". And "People should be kind and help each other (to survive as refugees since we're nearing extinction due to our own stupidity)". Finally, the taboo "DON'T GO TO THE LOST CONTINENT".
That was their bloodied writing on the wall when the survivors fled, and technology was lost, causing dark age regression. But due to political corruption over time, the power-hungry church central authority contorted that 180 degrees.
- Church glory-seeking hawks trampling on other "factions" of survivors/churches. Poaching awakened mages to assert dominion over weaker nations holding differing religious/ideological beliefs. Xenophobic-extremist misinterpretation of "Don't anger king class" as "KILL THEM ALL" against magic creatures (note: they are sapient vs beasts which aren't... see Shu's village. Also... take a guess who "El Magia" is). Misinterpreting/selectively hearing ambiguous prophecies from weak miko power holders, hoarded/kidnapped by the church over millennia.
- As well as the machinations of a pre-apocalypse (close to creation of world) secret society. Due to those immortals wanting to take revenge against the Church's and humans' idiocy, as revenge for people mistreated like Iris in the past. (I wrote a comment earlier describing what happened to Iris' parents.)
All this leads to the nation of Holy Grineer Church acting like a petulant child, going back to the abandoned continent seeking glory (once technology improves after massive timescale arc), pissing off those very sleeping giants again.... circumventing the original teachings. (Like they just did here with Shu.)
I've read WN pretty far (500 chapters or so / 6 timescale arcs of millenia) and there's a lot of lore.
