“[Progressive enhancement] was just an idea by a few niche people who wanted to disable 1/3 to 2/3 of their browser's technology then demand that web-site operators/builders spend a lot of time and money on implementing for that sub-1% population. They didn't, and these people had no real leverage.”
When progressive enhancement was the thing, nobody wanted to "disable 1/3 to 2/3 of their browser's technology", browsers mostly lacked many of modern CSS and JS enhancements across the board and having them fail graciously while still using modern features for the few who would support it was just the professional thing to do.
It sill is today of course, but it is obvious there are not many professionals left in webdev.