You're right about the A-4 being a good dog fighter. One of them killed a MiG with a rocket over Vietnam. That's like a Harbinger kill on a Dragon. I was mistaken.
The A-4 has no afterburner, though, and it would have a hard time staying on a modern fighter's tail. So since the EFs could easily evade, it's down to the Skyhawk's ability to do sufficient damage to the airfield to make it unusable. And they might just be able to get away with that, because fighters can only carry so many AMRAAMs and bullets.
If they had almost a wing of F-16A MLUs, though, with decent ordinance and logistics, they have a good chance of securing air superiority early on and then making it impossible for naval forces to come near the island. They just haven't bothered to make an investment that would allow them to pose a serious threat, despite considering F-16 and Mirage 2000 purchases.