Sure, the people making these things should feel bad about it, and ideally change their choices... But if 5% of Firefox users can't use your page, and your page

Sure, the people making these things should feel bad about it, and ideally change their choices... But if 5% of Firefox users can't use your page, and your page is important, they'll consider Firefox broken and go use something else. Firefox isn't doing so well on market share, and appearing to be broken isn't going to help.