See, this why I hate the term "frumpy". My new Munro sandals that I recommended to Suz definitely tick most of Aziraphale's "frumpy" boxes but I think they look fresh and modern. I hesitated to mention my Romika mules when Angie asked us about comfortable sandals because I was positive they'd be laughed off the YLF forum as irredeemably frumpy. I fell off my chair when Angie pronounced them on-trend.
I think "frumpy" is defined by the viewer and often is more about a personal poison eye than the design of the item--sort of an "I don't like it and wouldn't be caught dead in it" or (my favourite) " I wouldn't be caught dead wearing it because it looks like something my mother would wear" (why do I hear an adolescent whine accompanying that statement?).
Designs do become dated, and, if it's important to feel on-trend, I can see dismissing a style on those grounds. But it would be nice to see the commenter explain why the design of the toe box or heel is not on-trend (which Angie, by the way, does so very well) instead of just going "ooh, FRUMPY!" It was also nice to read Aziraphale's detailed description of what makes something "frumpy" TO HER. That way, we can agree to disagree. But calling something "frumpy"" and offering up up the "I just know frumpy when I see it" rationale bewilders me if the commenter is intending to be helpful.
Whew, felt better to get that off my chest. Signing off as a old lady resigned to wearing her comfortable sandals which she probably mistakenly feels are cool and stylish.