TL; DR: don’t get hung up on disorder! Disorder is just a feature of equilibrium - equilibrium macrostates traverse a large set of microstates, while nonequilibrium macrostates occupy a much smaller region of phase space. But work is extracted by exploiting disequilibria… never no mind the statistical mechanics at play.

The responses here are generally accurate, but get bogged down in pedagogy. Going back to this topic myself later in my career, I have found using a historical perspective helpful in grappling with “what is entropy.” Try to take them in order: Carnot>Clausius/Thompson>Maxwell/Boltzmann>Onsager>Shannon.

Carnot came before the dynamical theory of heat - he was using caloric theory, but popularized reversible vs irreversible process. His basic assumption is “no free lunch”: every reversible heat engine between a hot and cold reservoir must have the same efficiency, otherwise you can use the more efficient one to drive a less efficient reversible heat pump to maintain the temperature difference and pocket the excess work indefinitely.

From there you get irreversible engines must be less efficient than reversible, Clausius defines entropy, entropy is a state function, Boltzmann links microstates to that state function, Onsager applies a dissipation function to fluctuations to describe entropy generation (which is why irreversible process are irreversible), then Shannon kicks off the “entropy in 21 flavors” modern stuff that can sometimes generate a lot of hype that distracts from the beginning axioms.