the only part that breaks the suspension of disbelief here is the fact that almost NOBODY recognizes Frieren, specially town mayors and other head figures;
"but it's been a long time"
people know she's an elf, and know she'd still be around, there is absolutely no reason for her to not be one of the most famous and prominent figures in the whole world
"insolent elf! to the dungeons"
nope, impossible