I disagree, the action taken to create an extension and get it on HN sparks the discussion that can trigger real change. A boycott only works when you have a sufficient number of people doing the same, or in this case, a sufficient number of people bypassing the hostile UI.

Unfortunately lots of information is hostage to bad web design. I would really like to vote with my X button the web pages and apps of my uni, but instead I have to write scrapers to extract RSS feeds from their JS mess or else I can't know what's going on. Oh, the other option is to follow them on Facebook or Twitter. Also, the news sites often have hostile UIs, but one needs at least one of them.

In theory I agree, but reality makes that difficult to adhere to. To me, 15 minutes throwing a browser extension together is worth not being assaulted when I end up on a Medium-powered site. Same reasons I use an ad-blocker.