Earlier quoted context omitted.
https://openforest.fs.usda.gov/christmas-trees/forests has a pretty heavy dependency on Javascript (read: there's no fallback to anything non-javascript, so I get a white page). It feels like that goes against some of the things that 18F is about.
Pages don't need a fallback to non-Javascript in 2019. Accessibility technologies now fully support a JS enabled web, with accessibility standards following suit. That leaves only those who have voluntarily disabled JavaScript ( I've worked on public facing government websites (not 18F). We simply don't support this edge case, and our legal department supports our legal right to do so (in particular in relation to AD…
At this point, there is no reason to support Yes, if you're making a webapp, there's no good way to do it without JS and you can just be upfront about that. Also, people who can't use ES6+ are going to zero over time, so it's fine to just write ES6. But you should also have a no-JS fallback version of an information page (anything that's not a webapp) because that's an important usecase that won't drop to zero over time.