I must be out of touch, those aren’t fashionable and I don’t think most people in their 20s would think they are (sure they wear them all the time but that’s because of a rejection of fashion in favor of comfort.)
That's kind of what fashionable means.
Oxford dict:
Fashionable - characteristic of, influenced by, or representing a current popular style
I kinda like this Cambridges definition[1] of fashionable more (even if isn't perfect)
> wearing clothes, doing things, and going to places that are considered stylish
There is clear difference of what is considered stylish and what is popular.
Macmillian[2] has even more poignant definition available:
> popular with rich and successful people, and often expensive
Which I might disagree on specifics, but it still carries the thought over. Fashionable is not (necessarily, or even commonly) popular with the common people, but of some sort of elite.
[1] https://dictionary.cambridge.org/dictionary/english/fashiona...
[2] https://www.macmillandictionary.com/dictionary/british/fashi...
A lot of what is "popular" is still recognized by the wearer themselves as not fashionable, and is worn despite that (and sometimes because of that) for various reasons.