This got to be one of the most interesting threads I have come across so far here in that it blends two very intresting topics: retro loathing from bike sites and the politics of personal choices.
The way see it, I don't see bike sites loathing retro. On the contrary, just like several others have mentioned already retro is becoming a hot word that the bike industry (or a certain branch of it) and bike shops use to lure in clients. At least, that's my feel for Europe. Effectively, brands like Crust and Rivenell, or posts that show up in Radavist (and even in bikepacking.com some times) are heavily influence by retro bikes of the 90s. Crust has released bikes with quill stems, rivendell never switched to headsets to start with while Radavist documents really nice retro rigs from the Pro's Closet. Ultraromance paired with FTW to release an ATB too and soon a gravel bike.
To younger generations these brands are very appealing. I have lost count of how may restomods of old 26" MTBs that are now used as commuters I have seen here in Belgium in the last years. Their number, especially in big cities, keeps increasing. These are bikes that have been repurposed and although they are not speced in their original configuration they are very different from what most big brands sell you at their stores.
This all to say that retro is not loathed in the bike industry. Instead it has been used by brands that are seen to belong on the "alternative" spectrum of things.
I think the industry goes from modern (everything new) back to bringing retro parts and specs and the reverse in an attemp to keep itself relevant and appealing to clients. It's like the fashion industry, you need to keep reinventing the wheel and repurpose / reintegrate old concepts in your new products if you are to survive / sell.
That's my 5 cents a year and a few months late in case anyone cares! : )
