With swept wings attached to the P-80 the aircraft would have achieved higher speeds when nearing supersonic speed. Planes equipped with swept wings became less draggy while maintaining better stability due to high speeds. Better wings would not have been enough for the P-80 because it lacked sufficient engine power to achieve supersonic speed.
An aircraft needs more than ornate wings to achieve supersonic speed. Advanced materials combined with robust engines appeared only in jets equipped with afterburners and their arrival came much later.
The P-80 could have reached a higher speed with swept wings however its 1940s technology along with weak engines restricted maximum speed altogether.
The available technology during that period restricted engineers to use straight wings as their primary option. The P-80 served as a significant progressive development for jet aircraft despite its performance constraints.
