I may be prejudice, but the F-15E is a much better air-to-air fighter than the F-15C until it gets slow and tight.
My guess is that the “E” models got out “sticked”. The F-35s could get a radar lock and fire well before the F-15Es got their radar lock. There are tactics to compensate for the stealth aspect, but we don’t know whether these pilots were familiar with them or they were limited to 4th generation tactics. It is not a knock on the pilots/wso’s, the tactics are not widely known. We had some growing pains with the F-15Es and those had a proven aircraft to work from. So I understand the F-35 growing pains. If I were running the show, I would buy at least 50% F-35Cs. 35% more wing area is nothing to sneeze about (plus another 1,000 lbs of fuel).