The worthwhileness of the F-15X concept comes down to whether you believe the Air Force should pay to maintain a lower-tier force of cost-efficient fighters to handle missions that don't require the F-35's special capabilities, namely air defense of coastlines, munition hauling, and ground support in semi-permissive environments. However, those more preoccupied with high-intensity conflict scenarios with China or Russia will likely feel more skeptical of diluting the F-35 force to purchase older, less survivable jets.
Sébastien Roblin holds a Master’s Degree in Conflict Resolution from Georgetown University and served as a university instructor for the Peace Corps in China. He has also worked in education, editing, and refugee resettlement in France and the United States. He currently writes on security and military history for War Is Boring.