There was a good article from John Loeber a few months back about browser extensions: https://loeber.substack.com/p/9-15-years-of-market-gaps-for-...

He had the same point, where it feels like browser extensions are a big, somehow under-appreciated market. Browsers are huge platforms -- creating add-ons and making them more capable should be a popular, value-generating thing to do! But for a number of (developer) UX/UI issues, that just hasn't been the case. I hope this changes!