Sites can impose a Content Security Policy, that (among other things) can disable inline JavaScript. This makes it a real PITA to modify web sites with user CSS/JS.
I am personally aligned with pro-CSP because it can greatly reduce the attack surface of web sites I host, and is quite effective and precise.
Browser extensions can, and do, play around CSP.
Bookmarklets has no overhead in the browser, because they are just bookmarks that do not interact with the browser unless I click it. Having a little addon for each little functionality is annoying, slow, and difficult to maintain and review.
I am personally aligned with pro-CSP because it can greatly reduce the attack surface of web sites I host, and is quite effective and precise.
Browser extensions can, and do, play around CSP.
Bookmarklets has no overhead in the browser, because they are just bookmarks that do not interact with the browser unless I click it. Having a little addon for each little functionality is annoying, slow, and difficult to maintain and review.