Do you think the situation will improve while Firefox has 3% market share, down ~2% from 2 years ago, and with <1% share on mobile?
You're nitpicking, there are lots of corporate sites that only test against Chrome/Safari these days. I'd love it if Firefox would regain popularity, and Chrome would lose its stranglehold, but let's not stick our heads in the sand about the way things are going.
https://www.bankofamerica.com/information/supported-browsers...