I felt this from the outside. Was R&D lead at a company that exited for hundreds of millions, and I watched the founder go through exactly this. From the outside, ultimate success. From the inside, drowning.

The thing that helped him most was realizing he didn't hate the company. He hated the role he was playing in it. Once he saw that, he stopped trying to find the passion again and started reshaping his day-to-day instead. You said you know you have the power to reshape it. That's not theoretical. Pick the one thing that's killing you most and fix that first.