Moses I respectfully disagree the 109 was more versatille and could perfomr many ddifferent roles, the fact that it was in production until the Wars’ end demonstrates how important it was !
Stubborness on part of the Germans or their lack of ability to innovate? I give you one thing though, the 109 was a plane that could be easily be produced in mass quantities, though mid-late war the Germans needed better planes, not more of them (in a pilot-per-plane basis). Another shortfalling of the 109 was its lack of adequate armor. You could say this about the Spitfire too, but after Mark III (?), the Spitfire was significantly revamped.