I don't think I've seen much of what I'd call overt hostility. But there do seem to be a lot of firefox users commenting about not being able to use this. I don't think there'd be as many if the site wasn't saying that Firefox isn't supported because it doesn't support access to the local file system for uploads and downloads. But Firefox does indeed support that, just not via whatever API they're using.

It's just super weird to get downvoted multiple times for saying that I'm excited about something. I guess we won't call that hostility.

The funny thing is that for all of the people complaining about granting filesystem access, it actually won't allow you to select sensitive paths; no system folders, no drive roots.