Trouble is, the places that MATTER (i.e. schools which are teaching the children how to use a computer, and banks which are holding your money to ransom if you're anybody) don't give a shit. We're still fighting banks on "but this is more secure" when they make us run closed code in a closed plugin tied into closed sites on a particular browser that's not your normal browser and is - by definition - outdated. It shouldn't be.
No offense, but the biggest problem I've run into over the last year are web sites that use every damn proprietary feature of Chrome and try to itemize workarounds for every other browser. My problem isn't coming across web sites that still push Flash and Java, it's sites that are largely broken in Firefox and IE/Edge, and totally broken in Pale Moon.
Now that Chrome and the Blink engine are the most popular web technologies on the planet, I'm finding it hard to find sites that work in any other web browser that uses HTML5, no matter how up-to-date it is. Web developers need to get their heads out of their asses and make things that actually just work, not support only the absolute latest version of Chrome that was just released tomorrow.
The call for "standards compliance" from the early 2010's isn't fashionable anymore. Nobody gives a shit about HTML5 -- it's stupid, broken, non-standard DOM all the way down.