5th gens are way more radar reduced than they are IR reduced; note the various pictures of the IR-reduced F-22 and how they're obviously still visible. As I've mentioned elsewhere, one of the biggest advantages of VLO / LO is that you can stop a RF missile seeker from working until extremely close ranges. The missile will have to be data-linked until nearly the end. IR, since IR suppression is less effective, can go into autonomous mode far sooner.