It seems the most advanced physics engineers are using is basic quantum mechanics. Is it accurate to say this is the "final frontier" of engineering? The field of particle physics, for example, has been established for nearly 50 years now and there are still no practical uses of the incredible knowledge gained even though the amount of spinoff technologies in experimenting with these particles is countless. General relativity has been around for almost a century, and it has yet to produce any practical applications that directly require knowledge of GR and not corrections that could be approximated anyways. Of course, that's not the reason why physicists study these theories, but from the point of view of an engineer, is it safe to say these theories as well as any framework that goes beyond them will always be practically "useless" due to the fact that the energy levels and cosmological scales required to access for the phenomena of these theories to manifest will always be out of the practical reach of engineers?