I'm not understanding why people are so up in arms about this. I mean, yes I see the reasons, but I don't get the validity of them. Some people are upset that Apple is producing a modular/user upgradable tower PC but have priced it outside their economic range. But my question is, for most people (and Apple has all the use stats shared with it from the software phoning home regularly) I'd be willing to bet that there's no actual *need* for you to swap out drives or other things that go in slots. You may really really want to. And some of you may actually have that as a need. But I'd be wiling to guess that the number of people who have that NEED and are at the lower price point, is not high enough to justify an entire line of computers being built for them.
So, apple went with what works for MOST use cases - Mac mini for people who just want a desktop, iMac for people who need something more powerful, and iMac Pro for people who are pros but not $12,000 computer level pro work needs. Then, there's the top tier for people who are doing special fx and color grading n the billion dollar movies we watch in theaters, or magazines that are on newsstands, etc. Recording studios running 90 channels of audio with a suite of effects on each channel. That ain't the average person. That ain't the average person in this FORUM. An iMac Pro doesn't cut it for those folks and they need the pinnacle. But when they buy a dozen Mac pros at $25k a pop, they also need expandability so they last for the next six or seven years. Again, that ain't the average person, nor is it the average person in this forum. Hell, I don't need one but I WANT a pro display because of the design aesthetic, size, and specs. So I'll wait a few years and get one used for a couple thousand when it's time to upgrade my system again. But I'm not going to be mad at apple for not giving me what I want just because I want it because I want it.