> Just kind of strange that my entire career I was constantly told I needed to test this on any and all browsers available because they all have their nuances and you never know what might break something. To moving to a time where I'm testing on a single browser and calling it good? Man, times they are a changing.

Interoperability is hard. Plus there are network effects — and so that's why lots of ecosystems tend to see adoption of a single implementation as the de-facto standard. Remember when we had to be aware of character encodings that are not UTF-8?