Air combat is more to do with tactics and pilot skill than raw aircraft manoeuvring.
I don't think that anyone here is suggesting that the F-35 cannot perform air-to-air combat (not me, certainly), just that it does not appear to be able to deliver on its earlier promises of being a capable dogfighter.
“a single-pilot, survivable, first-day-of-the-war combat fighter with a precision, all-weather strike capability that uses a wide variety of air-to-surface and air-to-air weapons—and that defends itself in a dogfight.” John Kent, senior comms manager for the F-35 in 2003.
Both the Mig-17 and Mig-21 were superior "dog fighters" to the F-4/F-105 however while they achieved kills so did the USAF/USN.
Yes, but weren't the F-15 and F-16 born out of the experience of Vietnam, with a heavy emphasis on the ability to perform close-in 'dogfighting'?
The hard lessons learned (or not, perhaps).