It's efficient, sure, but Windows still effective counts as an open platform compared to Mac, because so many different vendors are welcome and involved. Closed vertical integration is worse for consumers.
And that consumer standard is also often based on price: Windows platforms are almost always cheaper than the Apple equivalent. So that efficiency doesn't benefit consumers.
I don't think either of those is necessarily a slam dunk. A lot of consumers really appreciate the non-openness of platforms like iOS when it comes to security, privacy, parental controls, and so on. I know your argument is specifically about the Mac, but on the "openness" spectrum, MacOS sits somewhere between Windows and iOS, so iOS is a helpful reference point for where the Mac could end up.
And as for cost— I don't think that's necessarily strictly worse either. I have a Dell XPS now, and it's.... fine. But relative to my old MBP, the screen is worse, the build quality is worse, the trackpad is worse, the keyboard is worse, the power management is way, way worse. So although there might be slightly more compute here in terms of the raw numbers, a lot of corners had to be cut to make this machine work out, and all things considered, I'm not sure that the market is in a better place when even "premium" non-Apple computers don't have the profit headroom to invest in the little stuff.
I'm an iOS convert, so you don't have to sell me on the benefits of a closed platform. But I was referring to more than just software. When servicing an Apple laptop with a broken keyboard last month, I had to find an Apple-brand USB keyboard in order to get it into the recovery menu, because I needed an Apple command key. (Linux works fine with the Windows key for similar types of shortcuts.)
The idea that I needed an Apple keyboard to do something trivial on an Apple machine was... hilarious to me.
Sure, there are Apple-certified accessories out there, but you literally have to buy stuff explicitly catered to their hardware for their software to work right. Whereas anyone else can use "literally any keyboard out there", you need an Apple keyboard to work with an Apple device.
And that consumer standard is also often based on price: Windows platforms are almost always cheaper than the Apple equivalent. So that efficiency doesn't benefit consumers.