You could fix the mobile site with as little as one line of CSS if you didn’t want to bother with media queries. `max-width: 100%` or `100vw` could be enough!
Funny, I've made lots of stuff responsive but at some point decided I had to have a minimum page width of 1050px.
Now when I remove that and add your "max-width: 100%" I don't see much of a problem. Sure, some content gets slightly misaligned on narrow screens but it looks pretty OK overall.
I just pushed the change now, should be visible within 5 minutes.
You'd be surprised how much code editing I get done on my phone these days - I ship small changes to my projects (including things like adding new badges to my READMEs) through the GitHub web interface quite often.
Being horribly old and needing glasses to see anything small but never having any glasses around, I find that my phone is pretty much useless for work. I guess I'm an outlier here. I'll just see what I can do to improve the mobile UX!
