Unfortunately, nowadays writing userscripts is much harder than it used to be. Most websites are using some sort of reactive FE framework so you need to make extensive use of mutationObservers (or whatever the equivalent is in jQuery I guess).
It's easier to write with LLMs. One-off projects (the way I treat userscripts) is where they really shine.
Oh the horrible things I do with Instagram...
Very true. I guess that depends on what websites you find issues with? I just checked mine and all of those are quality of life improvements for fully server rendered sites like HN or phpBB forums.
I often go for `setInterval` over `MutationObserver` because it works and I don't need instant reactivity and I don't have to think too much about it.