This is a beautifully written and concise essay, and it raises some fundamental issues. I offer comments on a couple of your statements for your consideration and thoughts.

1: “Here’s the problem: the exciton needs to randomly travel from one chlorophyll to the next to reach the reaction center, like a blind frog hopping on lily pads.”

There is nothing blind about a hungry frog when it sees a fly. Perhaps, like the hungry frog, the energized exciton is attracted toward the reaction center where it can transition back to a more stable and “happier” state, and in the process, releasing its energy to power photosynthesis. If I let go of a ball, there are many directions it might go, but there is nothing random about the trajectory it chooses. A system is always attracted toward a lower-energy state.

2: “When physicists measure such phenomena [quantum superposition] they need to work in carefully controlled environments to keep the wave in a state of coherence and to avoid it collapsing into a state of decoherence.”

A state of superposition, like Schrodinger’s live-dead cat, has never been observed for any macro or micro-state. It is a matter of assumptions and interpretation. I suggest that coherence and decoherence are not properties of state, but rather properties of process. The exciton is in a process of irreversible and random transition, from the moment it becomes unstable after absorbing a photon, to the instant of its “decoherence” back to a more stable and definite state. During transition, the exciton does not interact with its surroundings (or with any hypothetical measurement device), it is not observable, and I suggest that it does not exist as a state at all. This would readily explain a particle’s diffraction/non-diffraction results and the exciton’s abiity to maintain coherence during its transition within the plant. You can find more details on these ideas in https://medium.com/swlh/is-quantum-randomness-fundamental-633cb51f4d96.

I would welcome your thoughts.