There's a pretty big difference between embedded devices and high-end, general-purpose devices. Apple is very much the latter. Outside specific areas (like cell signal/etc) they are not constrained by hardware to the point that it inevitably impacts software quality—and the complaints people have are not about the parts of the software that are constrained! As far as I know, everybody is actually totally happy with Apple's wireless stack, power management and so on.

Now, is it possible that Apple's software issues are proximally caused by production pressure? Absolutely. That's almost definitely a major contributor. But the production pressure is not inherent to their device business; it's a choice the organization, collectively, makes.