it should be possible to make long lasting high quality clothing at an enormous scale.

Yes that’s what I said.

It’s a problem of economic motives

Yep

I would say that it was true about a decade ago…

Make sure to account for survivorship bias and your own luck and perception. Are you basing this off the fact you have stuff in your closet from that time? If so, make sure to understand there is probably a lot of stuff that broke from that time too.

There is also the option of niche brands producing good stuff.

And it’s hard to do that because of economies to scale. Their name implies they only sell socks.

Large scale manufacturing is not important IMO.

It’s not large scale manufacturing. I didn’t say that I said “stuff”. It’s vertical integration, large scale distribution, established brands, logistics, customer support, brand optics, etc. The sock company in your comment has “socks” in their name.