The DEFAULT one should be sane for most use cases though.
It was. "Enable javascript" was on by default.
But as most of the web these days doesn't work without at least some level of javascript,
Most of the web works just fine without javascript. Those times I had to disable it to get away from a page that was using it maliciously, I often forgot to turn it back on and found the "browsing experience" to be much more pleasant.
Saying that "most of the web doesn't work" unless you have javascript is another way of saying that "your web experience should be what I tell you it has to be".
having a dumb toggle default to either position is pretty much useless.
That's just silly. Having a toggle that defaults to "on" gets you your "javascript enabled" experience that you want newbs to have while still allowing others a choice.
But the global toggle would be useless unless it was in your face,
That's also silly. You propose a complicated by-page or by-site manager, but decry a simple "off" toggle as ... useless?
Think about ways of improving things, not ways of adding more options
I was already an option, quite simple. And it was a detriment to remove it, except to those who feel that controlling the viewer's "web experience" belongs in the hand of the site programmer and not the viewer.
that just cause things to break in yet more interesting ways.
I consider breaking malicious web pages to be a good thing. YMMV.