Most folks are not geeks with an inclination to tinker. We (as I am among them) want something that just works. Apple are more interested in satisfying most folks than pandering to geeks.
The solution I'd expect from Apple would be to make upgrades easy and (nearly) foolproof instead of preventing them. Screwless mounting of internal drives sliding right into the required ports. Access to Ram slots by simply opening a dead-easy bayonet locking mechanism. Oh wait ...
The reason I switched to Apple instead of Windows when I eventually had to abandon the Amiga, was that it simply worked, but still left some elegant ways to upgrade the machine when needed (think of e.g. the machine core with a handle in the Cube, the drive trays and practically cable-free interior of PowerMac/Mac Pro or the simple turning baseplate on the minis from 2010 through 2012).
I also want a machine to simply work, but at the same time I like to upgrade every now and then. And I expect a premium brand such as Apple to find elegant solutions to that for their premium-priced products and especially not to _remove_ existing solutions (like the mini baseplate) without at least trying to communicate that change properly. And no, I don't feel a single slide with a rushed 1-minute-"oh by the way we updated the mini you can read the new specs on the slide behind me"-poor-excuse-of-a-presentation as anywhere even remotely adequate!
As for the soldered RAM - [...] driving down power consumption, at idle and under load, is one of Apple's ongoing goals. [...] And it was the power saving that drove the decision to switch, not a desire to screw over Mini Buyers.
And why did that switch require to redesign the baseplate and make it unnecessarily more difficult to get into the machine? That surely did cost time and money for engineering hours and changing production tools. And for what? People who don't upgrade, wouldn't bother to look inside the machine anyway. And those who do, would understand if they wouldn't see a Ram socket after opening the baseplate.
But most of all: If the switch was really motivated by power-saving reasons (personally I rather believe that the Mac mini dev team has to swallow whatever the Macbook dev team decides) - why can't Apple communicate that properly either on stage or at least via Website/tech blogs etc.?
The 2014 1.4Ghz Model was [...] not about deliberatly downgrading the Mini line. [...] The few people I know at Apple [have] implied, without specifics, that Apple's current generation of computers were impacted by Intel's schedule and production problems with 14nm/Broadwell.
I chose to take that to mean that what Apple's done with the 2014 Mac Minis was not about downgrading it's potential, but making the best of what was actually available CPU wise.
To me that doesn't explain why they ceased to produce the quad-core from 2012 instead of offering it in parallel to the redesigned 2014 model. They did so more than once in the past, e.g. during the Retina transition of the MBP's or with various education iMacs. They could've easily done it again for the mini to help lessen the claimed impact of Intels production/schedule problems.
Sorry, but I don't buy the story of the poor Apple guys being helpless victims of evil Intel's production and schedule problems, but heroically going to great lengths to make the customer experience still as good as humanly possible under the given conditions.

Admitted, the final decision was probably made by some higher-level manager at Apple (perhaps even Phil Schiller himself) and not the actual engineers, but still ...
Just to make it clear: This is NOT against you being only the messenger!