While "intermittent refresh cycles" are certainly a thing for the Mac line recently, I think it's important to distinguish "new features that seem to be flops" from both "no new features" and "not caring about the Mac line." The Touch Bar may or may not be a dead end (I don't hate it the way many other people do, but if it went away I wouldn't shed a tear, either), but it represents a significant amount of engineering work put into a Mac-only feature. So does the love-it-or-hate-it† "Butterfly" keyboard. And the new ARM-based T2 chip, which handles tasks from encryption to signal processing to being the SSD controller, is also obviously significant engineering -- and again, Mac-only.

I don't doubt that Macs will eventually fade into the sunset, but I don't think it's coming nearly as quickly as either pundits or pessimists seem to believe. "Marzipan" may indeed be a first step, but I think it's going to be a Carbon vs. Cocoa situation, taking many years to fully transition. For iOS to supplant macOS, it has to essentially do everything macOS does. It doesn't have to do everything the same way, but if it's going to be a full replacement for a general purpose computing platform, it has to be, well, a general purpose computing platform.

†Technically, "grudgingly-tolerate-it" should be in there, but it doesn't flow well.