[pjc50]

Exactly. Backwards compatibility is king. There have been plenty of research operating systems which never made it to popularity; not just Plan 9 but things like BeOS and Nemesis. The network effects driving people to consolidate on one system are huge.

Browser design is a mess, but that's because it's a battlefield between competing demands. We're very lucky it's remained open and competitive. There's an alternate universe somewhere where IE6 won and you have to use ActiveX controls to enter your government ID before you can post to websites. (Oh wait, that's South Korea in this universe http://www.bbc.co.uk/news/technology-29617196)

You can write a better operating system, but unless it runs a browser and you can give it away for free it will have a very limited audience.