From what I recall, there will be no easy energy once our civ dies out. Whichever civilization rises after us, it will face a limit to what heights it can reach.

Part of why it'd be better to have a reset back to the beginning of evolution, so everything can happen again over all those years, and also so there are 0 traces of "tech" or trash from the past ~400,000 years to present to corrupt them. Although there being no easy energy would trigger innovations as well that'd blow all we've done out of the water, with the historical knowledge of why their predecessors became extinct and so aim for a better path to avoid that fate.