older jets with new equipment

I’ve long argued that in modern air combat, technology trumps design

so what are the thoughts on this?
how would say an F-16A upgraded with the latest missiles, radar, ECM, optical sensors and DAS fare against an Su-35 or T-50?
how would a Mig-21 with the latest toys do against an F-15 with the latest tech, or even an F-22?

I would argue that if you give any aircraft AESA and/or DAS (that can detect any (stealthy) aircraft WVR at 360 degree) and advanced (optically guided) missiles (like the Python 5), it means any aircraft with said sensors and weapons could instantly engage any aircraft WVR (which I believe is one of the F-35’s biggest strengths)