> Developers wrote and tested their sites for and with IE6, and were then surprised they rendered (in)correctly on Firefox and looked wrong
But that's the point: rendering shouldn't really matter. For things that are important like government systems, we should treat web "apps" much like TeX encourages: you specify the semantics, and let the rendering engine do what it will. Don't try to precisely control it. You can and should assume that users can totally override rendering with a custom agent, that browsers will disagree on default rendering, and that they may ignore your CSS instructions.
Like if someone wants to use a browser that always renders h1, h2, p, etc. with specific fonts and colors, totally ignores any CSS, and adds buttons to each table column header to sort on that column, that should all just work. Or if you want to use a braille output or screen reader.
For important tools and information, not entertainment/shopping, functionality should trump all other concerns.
My bank and now my power company have issues where I need to use chromium to fill out a form, and I don't understand it. I know Firefox supports forms. For whatever reason, javascript is loading the thing and screwing up somehow. I don't see why js is even involved, but frankly it screams incompetence to me. The easiest thing in the world to build, and they've broken it trying to make it look nice.
I don't go to my power company website for fun. I'm there to pay a bill. I need a form with 5 inputs and a submit button, and that's it. The rest of the screen can be plain white for all I care. Literally something I could put together in 2 minutes when I was 11, and it does not work. Paper should not have a better UI than a website.
Incidentally, this is why I'm not too worried about AI. If companies wanted cheap/easy/reliable systems, that's been doable on the web the whole time. People can't resist making things difficult for themselves, and they'll pay very good money to do it.