[goatinaboat]

what's wrong with just using the jets we already have.

Two words: metal fatigue. Every airframe only has a finite amount of hours it can fly before its structure becomes too weak. Fighters in particular that regularly perform high-g manoeuvres. So they have to be replaced anyway.

The war in Afghanistan saw Western militaries burning off airframe-hours at a phenomenal rate using expensive fighters designed for neer-peer conflicts to drop dumb bombs, when you could have done the job for a fraction of the cost with simple propeller planes like https://en.wikipedia.org/wiki/Embraer_EMB_314_Super_Tucano