plawolf
Lieutenant General
Military aircraft of the 50s and 70s are not obsolete. It is continually improving. China can integrate AESA radar into the Mig-21 if needed. But the better way is to convert the Mig-21 into a UAV.
You are forgetting that India is not China. They could not even make a 70s era Mig21 right now without foreign help, and a lot of it.
They cannot afford to pay through the nose for foreign fighters, even ones they are assembling locally under licence, and their much vaunted LCA is proving to be even more expensive than foreign imports but only have a fraction of the capabilities. That’s why they went with that ridiculous Bison upgrade when literally no one else would touch that nonsense with a barge pole.