"The non-critical-of-Apple reading is convoluted and tortured, imo."
Perhaps you are also reading things with a certain context - "poor", "convoluted", "tortured", "lack", "can't" - all negative words used in this comment. People often see things through lenses, - if management is negative, thin skinned, looking at a statement like that as anything but an indictment of the company would be wondrous.
As others pointed out, the context of the letter speaks very differently. Whether it is "Apples" river or the river of inspiration of the employee, is hardly worth arguing over, inspiration comes from without and is experienced by the employee, there is nothing innately inspiration about a company, ever, only about its employees...who make up said company.
I suppose you might want to argue that employees can inspire other employees - perhaps, but only to the limited degree which some employees have different experiences than others. As a senior employee, you are somewhat expected to be that source of inspiration, saying rivers dry up, e.g. yours, is not saying that Apple the company, can never be a place employees will experience inspiration, just that you aren't experiencing it anymore, and that's perfectly fine.
What's also perfectly fine is that management reacted this, way, which, ironically, foreshadows the absolutely lack-luster dumpster fire which was Apple in the past decade. It illustrates perhaps why there was not inspiration, because leadership failed to provide it.