Even su-35 has a very good subsonic ITR but mediocre subsonic STR : (supersonic ITR and STR are terrible such as fuel economy,very draggy platform )it seems russian can achieve only designs optimized for era of limited angle wvr missiles…At least this mig mig21 looks like a moderate negative stability design, (opposite to modern sukhoys) ,a concept totally exploited just in recent eurocanards (particullarly in eurofighter) and abbandoned in more “modern” soviet design (except for the mig-35 prototype)