Interesting piece. You probably didn’t mean it, but actually I’ve gone the other way and come away thinking Apple have made the right choice here. If Mac went touch enabled, the expectation would be that iOS apps would run on Mac. Currently they can’t. Likewise, they would somehow have to work convincingly in that environment. They don’t or wouldn’t because they’ve never been designed to work that way.
It’s also natural to assume UI elements would have to take their cues from iOS, but do they? There would be so many design trade-offs: loss of functionality, loss of scalability etc. There’s an in-built assumption that iOS-ification naturally means a good Mac touch experience.
It forgets a fundamental advantage of macOS over iOS — drag and drop. It makes my work so much simpler, but most iOS apps are not drag enabled. They are not party animals. Mac is designed with multitasking and interoperability in mind. It is the party.
When I look at that iOS style multitasking window, I feel that you’ve missed the point. What the Mac could do with isn’t iOS touch elements that you wouldn’t use (touch would probably be used in an occasional way) but a UI that anticipates what I’m doing when I’m working interoperatively — everything from how I manage my windows, to bringing the correct window forward when I’m dragging an element from finder or another app. In order words, to deepen that interoperability, not limit it for the sake of unified aesthetics.
To me, you’re thinking about the problem the wrong way round.