I'm having a hard time finding it, but there's a quote from a famous physicist along the lines of "we already have a theory of everything we encounter in daily life, it's just that we can't apply it to practically anything". For instance, we still have no idea how unconventional superconductors work. Of course, they're completely described by plain old quantum mechanics without even using field theory. However, that still doesn't mean we understand them because the theory is too complex.
I'm personally interested in the rising complexity frontier of physics where increased computing power and new methods of approaching problems will help uncover emergent phenomena. Plus, there's other accelerators besides colliders that are essential to this field (x-ray light sources for instance).
We should come back to the energy problem experimentally when we can affordably make a revolutionary accelerator (like x100, not a factor of 2 or 3). That will come when we have mastered advanced acceleration techniques like plasma and wakefield.