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.)
Rejection of fashion in very specific trendy ways is fashionable right now. It’s more a rejection of “runway inspired” trends than a rejection of fashion itself.
In this current internet age, there's a lot of trends of fashion. There was even a trend called normcore (https://www.highsnobiety.com/p/what-is-normcore/) that rejected typical fashion trends at that time.
Is it not art to demonstrate the capability of the designer? And what’s expected to follow is that they can put a great looking “regular” item together too
fashionable, popular, trendy, and common all mean different things even if they are somewhat interlinked concepts. High fashion then stands even more apart from the rest.
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.
The important aspect of what.you describe is that fashion is more aspirational than popular.
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.
So wear your pajamas, if comfort is the only thing that matters.
P.S. class aside, nylon is a bad choice to wear on an airplane. It melts into your skin. Cotton and leather are good choices if you want to survive an accident. Also decent lace up shoes can save your life if you need to exit a burning airplane. Try running over burning wreckage with flip-flops.
I take off my shoes for comfort when at altitude, but lace them up for takeoff and landing.
High fashion is always copying what the regular unfashionable people on the street are wearing, in the eternal search for authenticity.
Which is why things like bubble jackets, sweat pants, crocs and dad sneakers evolved from being laughed at to being very fashionable.