But a lot of the F-22 capabilities except for the flight envleope and stealth could be put into F-15's. Just look at how the Russians have updated their MiG-29 with vectored thrust engines and improved avionics to created the MiG-35. It wouldn't have been any cheaper to develop those technologies, but they wouldn't have lumped all into the F-22 program.
I believe that research tests of an enhanced F-15 with canards & thrust vectoring nozzles were done years ago(probably by NASA-not sure).The Mig-35 is a Mig-29 on steriods.It will still be hobbled by it’s range,weaker radar capacity as well as poorer supersonic performance vis-a-vis it’s new European rivals.You can’t expect a boosted F-15 to do much better.