Yes, Ukraines airforce is bullshit. Practically non existent. That changes instantly if they get F-16s. I dont think you are fully appreciating what air superiority means for a military force at war.
You are really overstating the impact of these old F-16's. The radars are obsolete, and they will be flying nap of the earth, just like the current MiG-29's.
They will
not be roaming over the front lines freely, dropping JDAMS like it was Afghanistan or Iraq. Ukraine ain't that way.
The Russian Su-35's and MiG-31's have more powerful radars and a long range AAM that will let them see first and shoot first, while staying out of range of the F-16/AIM-120C. The R-37 is already proven very effective with several kills on AFU fighters.
The F-16's will NOT provide air superiority to Ukraine. What they will bring is a fire-and-forget AAM that will help them defend against the Russian cruise missiles and Shahed drones, and the capability for JASSM, which is similar to the Storm Shadow. That would alleviate (at least partially) the lack of ATACMS and give the AFU improved deep-strike capability.
These Block 20 MLU's could (in theory) take radar data from Patriot or another long range radar to cue the AMRAAM, and just not use the APG-66 which would give away their position. But to do that, we'd have to let them into the Link16 network, and it's debatable whether or not we'd go for that.
It's an incremental improvement over what the AFU have now, but definitely not a game changer by any stretch.