You are totally discounting Portable SAM systems , if you check any war, aircrafts lost in Ground fire ( SAM , AAA Guns ) are almost equal to aircrafts lost to other jets , Stealthy F-117 in First Gulf war made USAF Invisible due to lack of technology to Detect Stealth in 80's but Radar technology has changed over the years and detection and counter anti stealth technology are in place today .
I did no discount portable SAMs, in fact I explicitly mentioned them in my post, in a paranthetical remark. As I said, they move only as fast as the trucks they are mounted on. On the other hand, the radar and missiles mounted on a fighter move through the air at the speed of sound or more. If you have a portable SAM protecting Mumbai, and you detect hostile airrafts over Pune or Nagpur, can those SAMs relocate to those cities in time? On the other hand, if you have mig 29s near mumbai, they can fly to Pune or Nagpur in a few minutes. And how do you transport portable SAMs through places that don't have a road network? There is no comparison, fighter jets provide the best protection against other fighter jets.
Technology has evolved on both fronts. Countermeasures, as well as counter countermeasures. As I said, once the SAM is detected, you can send a cruise missile or bomb at it. Once a particular SAM site is destroyed, your aicrafts can pass through. But availability of enemy fighter jets pose a much bigger challenge. Remember, SAMs are not invisible either - they always announce their presence by emitting RADAR waves.