I'm probably missing your point, but I don't mean in the sense of them being a common type of footwear, I mean they were on runways, worn by celebrities, etc. https://www.whowhatwear.co.uk/crocs-shoes/slide4

My point was just that they definitely were a thing 15 years back. Whether they're more fashionable now or then: no idea, neither do I care much :-)

Ah. I forgive myself for not parsing the point made because that is a non sequitur

Point was that 2021 fashion was rerun of a past trend.

Sure, but there's nothing new under the sun. And ironic fashion is still fashion.