I'd like to remind y'all that this has been the art style since chapter 21,for the previous artist themselves retired from the series after chapter 20 marked the end of volume four.
If we take that at face value,instead of a cheaper cost,it could be that the previous one was either not happy with an aspect of the work(pay too low,too much interference,unrealistic deadlines,etc.)or something personal came up,speculation unless someone can find a corresponding answer.
But as y'all can also see from the art tab,they've reached volume eight(probably up until chapter 40)with this artist(albeit,volume eight itself looks different)for this 2020 starting comic,so at least the story still holds up for them to get serialised to that extent.
Grit ye teeth,stick to ye guns,and polish those peglegs,for these are the high seas we've been left with.
At least the characters' designs didn't change all too much,real whiplash is when you compare "Demon Lord,Retry!" and "Demon Lord,Retry! R",which at least also kept the good story.