Wash your clothes the old way (starch-based slime, naphtha soap, hot water from the stovetop three separate times, borax, bluing, etc.) for two weeks and let me know how you feel.
I know you don't pay attention to the details of a series, but it is also consistent with Frieren and Fern gushing over the pots and pans cleaning spell at the beginning of this long-ass arc. A spell they were both very happy to acquire and one they both considered to be one of the most valued they'd found over the years.
It's not a meme, it's one of the smartest gags the author has done in the series as a whole.