I am open to dropping support provided our html fallback is in place.
What we can certainly not do is show a working static page to ie9 and a broken page to 1 year old Firefox.
I prefer to just transpile up to say 2-3 year old Firefox / Chrome, but am happy to leave that call to @eviltrout and you, we can go more aggressive I guess, but we can not display broken pages
Edit, see backlink, this can be a pretty serious issue on android that tends to have terrible cadence upgrading browsers