Well, I am disappointed in the slow roll-out of new Macs too, but in all fairness, this decline is probably driven by lower iPhone sales. A huge proportion of Apple's revenue comes from the iPhone. Last year, there was pent-up demand for a larger iPhone, which was satisfied by the 6/6+ release. No way the 6s/6s+ was going to duplicate that year's sales.
That goes to the heart of the issue here. Under Cook's tenure, and spurred on by a board that, like most, only cares about operating margin and profit for the next quarter and not the next twenty, Apple has transitioned from a dedicated niche provider of great products that had a successful mass market device to a mass market merchandiser using its old 'rebel dreamer' cachet and admittedly second-to-none marketing machine to charge absurd margins for them. That's sustainable only so long as you don't have a mature market, where the product category has been whittled down and rigidly defined over a succession of generations, being wildly innovative at first before that decays to conservative spec increases. Personal computers have been there for a long while, and Apple tried to to what Apple does when their margins are suppressed by competitors who see their success and copy them with 70% of experience for 50% of the cost: find a new product category. Their embrace of the 'post-PC' rubbish, and it is utter rubbish, was not because it believed dedicated personal computing was dead but because they could no longer compete in that space whilst maintaining both their margins and their profits. That's Apple eternal failing: they fight against innovation, because innovation is inherently deflationary. The same technology over time will always cost less unless there is either a monopoly or criminal collusion.
If they ever want to earn back their acclaim and their dedicated audience, they need to relegate iPhone back to what it should be, an extension of their platform and not the cornerstone. They need to stop truncating macOS to duplicate the look, feel and feature set of iOS. If they want professionals, ones who have the passion for great products and the discretionary income to match, they need to remember what built the house, not what put the granite counters in the kitchen.