The high concept of a show is usually found in its character archetypes, not a “big idea.”
Shows are about a family, de facto or otherwise. Show the dynamics of that family.
Most spec pilots get this note: cut all this plot into the first act, explore the situation in the second, third, fourth act – odds are the pilot will be your only time the characters exist, don’t save anything.
Pilots usually work like this: ordinary world (setup character dynamics)/ break from expectations (explore the dynamics via chaos that follows) /new status quo (sets up dynamic that the rest of the season will explore).
Avoid premise pilots. A pilot should feel like an illustrative episode of the series, not a completely separate story that fails to set up what you find interesting about the concept and cast.