incompatible extensions ( yes i realise this is NOT Mozilla's fault)
the
Actually... it is. Think of it this way.
An application is sort of like an "extension" to an Operating System.
Windows has been changed a LOT more than Firefox has and yet can still run most programs from 1995.
Firefox has made far fewer changes. The only reason extensions don't work is because Firefox will yell that a plugin is "incompatible" if the plugin doesn't declare compatibility with the current version. Even though absolutely none of the changes made to the browser can possibly make most plugins "incompatible" because they don't affect the "surface" that plugins and extensions can deal with.