Some specific criticisms are out of date, but the gist still seems true.
On the off chance any Mozilla people ever read this, the feedback has uniformly been positive about the piece. If any of you still harbor delusions of platform-ness, it's not going to happen. The developer community has been burned. I don't think we'll ever trust the Mozilla team to promise us a platform again.
If I could say one thing to the Mozilla/Firefox project, it would be this: You are a browser. You will never be anything else. When you're not being a browser, you're being a web-app (Thunderbird et al). Start simplifying. Drop RDF. Stop pretending XUL is anything but a browser-creation DSL. Simplify XPCOM. Do this conciously, and go over every abstraction and ask if you really use it or if it's there because somebody, somewhere might use it.
But it's probably too late for that.
(To be fair, I haven't heard about this from the project for a while, but I still get the sense the heavy-duty design pervades the project, now with its reason-for-being lost in the mists of history.)