&gt;  The whole XPCOM and XUL legacy API cruft do hurt Firefox.<p>I&#x27;d argue the exact opposite - that &quot;cruft&quot; is the reason I still use Firefox. Extensions are so much better because they can truly have native features and have deep access to the browser. From the native look and feel of the LastPass extension of Firefox to basic stuff I need like sidetabs are only possible because of this deep &quot;legacy&quot; API rather than the extremely limited web based APIs everyone&#x27;s pushing for these days.<p>Kill XPCOM and XUL and you kill the only reason I still use Firefox.<p>At least in the current state of things, nothing to say they won&#x27;t improve the web-style extension APIs at some point but they&#x27;re really not ready yet in my opinion, they&#x27;ve got a long way to go and leave a lot to be desired.