A professional B2B car parts dealer has a very different user profile than say, a local news site in rural Africa.
A site selling concert tickets (for popular artist) probably won't care if site doesn't work for 5% of visitors, the tickets will just take a bit longer to sell out.
But otoh I'm sure there's many businesses out there who wouldn't mind a 2..5% bump in conversion ratio for very little effort.
Personally I don't care. If I'm out to buy something online & webshop doesn't work or takes too long to load, my purchase goes elsewhere.
And ofc government services should be very conservative in this respect.
Edit: and yes, graceful degradation. It's ok if site doesn't look as intended but is still useable for that 2%. And eg. I love that some news site have a text-only lite version.
It kind of makes me wonder if anyone has made a build system / framework that serves nested CSS to modern browsers, and falls back to a preprocessed CSS file that removes all the nesting for older browsers.
What they say is that you have to ensure that your site still works for the remaining users, through graceful degradation.
If people have new fancy browsers, use their features to make the interface jazzy. If they don't, ensure that the site still offers its core functionality to them without the fancy features.
WebP is especially hated for this among non-techies (31.8k upvotes, 1 month ago): https://www.reddit.com/r/mildlyinfuriating/comments/1trpuvr/...