But, iOS 11 is a dog. A buggy, wet, smelly one. So while most of their income comes from iOS devices, this doesn't in itself explain the decline in quality for Macs because it has been a decline across the board.
It was a step back from iOS 10 on older hardware. I upgraded an iPad Air and iPad Pro first gen and the UI stuttering/stalls makes both machines feel slower. I decided beforehand not to even try on the 5S, which was a good decision except that Apple constantly nags to update and downloads the entire 1.1 GB update file to my 16 GB device without asking me (yes, I have background App updates turned off) and forces me to delete it manually to get storage back. It's infuriating.
I think your right. But if the idea is the halo effect that keeps me in the ecosystem, they need to do better on the OS/laptop front and on the Siri front. Both are slipping.