F-15E Strike Eagles have advanced avionics and can and continue to use advanced missiles. They can serve in multiple roles including target identification, aerial combat, and of course air-to-air interception and ground attack roles.

Same thing with the F-18.

Eventually of course all of these weapons platforms will be phased out, but for the time being they are still extremely useful, and even more so after the more advanced aircraft and other attack vectors have taken out or limited air defense capabilities or the ability for enemy aircraft to intercept these aircraft. Not that they can't handle their own, anyway.