Ultimately this is a super minor issue (and turns out there's a way to fix it, per the sibling comment), but everyone just has their own pet excuse why they "can't" change to a browser that is objectively better for the web in every way.
Tragedy of the commons, I guess.
Aside from that I don't think Firefox is particularly good for the web. Their license is no better than that of Chromium, and Chromium has proven time and again it's a good starting point for a fork.
Mozilla employees are paid with search ad revenue, to an even greater extent (95%) than the subset of Blink developers employed by Google -- so their incentives aren't even any better.
You'll have to prefix your searches with a key (in my case it's w for wikipedia, g for Google, and so on), but that's what I prefer personally anyway.
Also set browser.fixup.alternate.enabled to false to prevent Firefox from retrying whatever you have typed in with a .com suffix.
Strangely foo/ works (goes to http://foo/) while foo/bar does not (instead does a web search for foo/bar).