You won't go far with Chromium or WebKit on their own, and Firefox remains to be seen if it is still around in a decade.
Which will end the day Apple is forced to allow Chrome on iOS.
In the anglosphere and averaged out globally, yes, this is true. But country-per-country, the stats vary wildly. Some countries have ~20% Safari usage, others have ~20% Firefox usage. Other countries like Germany for example has Chrome usage below 50%, which is pretty neat.
But yeah, if you're a Usaian, I could understand if "the world" looks differently.
Only best effort, not a requirement.