JS has been made less shitty. I’ll give you that old JS was pretty shitty. Like v5 and lower were a huge pain. But a lot of that was because of the lack of modern language features that other languages had at the time. ES6 introduces some huge improvements that made JavaScript much less frustrating. Personally, at this point, I have very few pain points with the language.

I don’t think being included in browsers is the only reason JS became so popular, but it’s definitely the biggest reason. That doesn’t make it a bad language.

Backwards incompatible changes have been introduced in JS a number of times. They are opt in at the script level and enforced in newer language contexts.