Yes, but most users don't take responsibility for the extensions they install quite that way.

The problem comes if you install a browser extension (or acquire malware that installs a browser extension for you), forget about it, and then blame the website when the website stops working, often filing bug reports (increasing the support load of the website).

And don't forget the bad-mouthing on social media.

Just look at hacker news. Many posts have someone complaining how the site is broken only to find out they have disabled scripts or have a night mode extension, or disabled webgl but forgot about it, or they programed their router to drop all packets that were going to a url that included "google" anywhere in it (including mysite.com/google-blog-post, true story)

So basically you're ok with randomly getting broken pages if you use content-modifying browser extensions? If yes, no problem. If it's an issue - something's got to give.

Simple answer: Yes.

Longer answer: I install any such extension with full knowledge of their potential to cause breakage, and consequently my first reaction to a broken page is to issue a reload with the extension disabled.

The web being programmatically accessible and end-user-malleable is a strength, not a weakness.

But many (I'd put my money on "most") users' first reaction isn't to issue a reload with the extension disabled. A lot of users aren't even aware of what extensions they have installed, and their first reaction is to file a bug report to the website.

It would be nice if there was some way to prevent users from reporting bugs if they have extensions modifying the website in certain ways, or at least warn them to try disabling their extensions first. I wouldn't even mind a whitelist for certain well-behaved ad blockers, but certain extensions are well known for being bad (many extensions _inject_ ads, which is a recipe for website breakage).