Earlier quoted context omitted.
Consolas is not bad. DejaVu is not bad. Only Courier/Courier New are so bad as to be unusable, it seems Apple wants to push web developers to use font overrides.
DejaVu is not a websafe font, meaning you cannot rely on it being available. Why we can't just require browsers to include DejaVu or another open font is another question - not like the size matters compared to all the other crap they ship. Heck, some even ship their own fonts already, but only for emojis. Even having some defined meta fonts with rough metrics so that you could say font-face: monospace-standard or wh…
Including a small set of open fonts does seem like a good idea. I'd like to see Inter UI[0] included because it's a very nice screen/UI-optimized font would serve a similar purpose as "system-ui" does now, except without some of the pitfalls[1] that comes with.
[0]: https://rsms.me/inter/ [1]: https://infinnie.github.io/blog/2017/systemui.html