A fleet of Mig-21s, even upgraded, would be no match for F-35s. Even using Su-30s as a mini AWACs, the F-35s wouldn't be detected on radar. So the F-35s could wax the Sukhois, and then take on the blind Fishbeds with ease. It would be like what the F-22 pilots call it when they went up against 4th Gen fighters; clubbing baby seals.
Fishbeds are decent jets in terms of speed and agility, but they're not dogfighters; they have horrible visibilty, they bleed energy in turns (delta wings), and they have limited weapons carriage.
I like the F-22 for Air-to-Air. I think the F-35 is probably okay, just not remotely worth the money. But I think our "all in" on a single do-it-all, super-expensive fighter-bomber is a huge risk and the wrong direction. We need a mix of assets. And unfortunately, the F-35 just eats up the whole budget so we can't afford anything else. It definitely shouldn't be doing CAS, and strike is probably best performed by other assets too. Trying to merge AF, Navy, and Marine planes into one super plane is bad for so many reasons.
The whole plan seems incapable of taking on serious adversaries and incredible overkill for insurgency operations. A no man's land of happy defense contractors and bad military strategy.
I agree with the parent in that a diversified set of aircraft focused on specific missions and more easily produced and upgraded with new tech is critical (no ones saying build bi-planes). And sure we can say 4th-gen beats 3rd-gen and now 5th-gen beats 4th-gen, unfortunately adversaries often don’t follow the script. F-35 seems to be more a danger to national security than a help.
[1] https://en.wikipedia.org/wiki/S-300_(missile) [2] http://forum.keypublishing.com/showthread.php?121375-MiG-21-...