> Originally Phoenix was the Gecko engine in a native UI window without all the XUL overhead
I'm not sure Phoenix was ever a reaction to XUL. Phoenix was more a reaction to the kitchen sink feature-list of Netscape 5 and Mozilla Application Suite, seeking to pare down the feature set to a minimally viable browser.
In XUL (and moreso XBL) Mozilla had a web technology that there was talk of submitting for standardization and which brought with it a level of expression that HTML didn't offer at the time. As HTML, CSS and JavaScript have evolved, XUL/XBL bring less and less to the table.
I'm not sure Phoenix was ever a reaction to XUL. Phoenix was more a reaction to the kitchen sink feature-list of Netscape 5 and Mozilla Application Suite, seeking to pare down the feature set to a minimally viable browser.
In XUL (and moreso XBL) Mozilla had a web technology that there was talk of submitting for standardization and which brought with it a level of expression that HTML didn't offer at the time. As HTML, CSS and JavaScript have evolved, XUL/XBL bring less and less to the table.