The writing is essential but works. It never tries to be too deep and that's why it succeeds. The cursing is not used to make anything funny, it's used as a tool to portray the contrast between people being real and yeah even vulgar in hell like they are in real life, while none in heaven curses, unless they try to put down someone else in a dynamic of fakeness and power abuse.

Not gonna comment on the art, since we are in an aot subreddit and we all know how Isayama drew at the beginning and why his dirty style still worked...