In a military context, the main technological gaps relating to jet engines are supercruise and maintenance hours. Both are potentially quite relevant in a ‘local’ conflict.
I'm not sure about maintenance hours. That matters as a function of proximity to maintenance staff, parts, new supply and so on. Flying from home bases, with no shortage of skilled labor can cover that.
Supercruise also matters a bit less when the distance to combat is shorter. Less fuel expended on "getting there" is more fuel for "on station". Plus, assuming more-or-less unlimited supply of machines and pilots means more flight hours on station.
So while the engines play a part in a hypothetical conflict, supply lines (and the length thereof) play (I think) a larger part.
I'm not sure about maintenance hours. That matters as a function of proximity to maintenance staff, parts, new supply and so on. Flying from home bases, with no shortage of skilled labor can cover that.
Supercruise also matters a bit less when the distance to combat is shorter. Less fuel expended on "getting there" is more fuel for "on station". Plus, assuming more-or-less unlimited supply of machines and pilots means more flight hours on station.
So while the engines play a part in a hypothetical conflict, supply lines (and the length thereof) play (I think) a larger part.