A computer like the Mini should get yearly updates - and there is no good reason to solder in the memory. While it kept the very same design, it went from a quad-core i7 to a dual-core, with fixed memory. Which then stopped to be upgraded.
The versatile Mac Pro got replaced with the current can-like design, limiting the choices and then never got upgraded. If you make a machine which cannot be user-upgraded, please upgrade it every year. There is no good reason, there is no option for the current NVidia or AMD cards available.
The iMac is still one of the better offerings - I got the 5k after the last refresh. However, while this gives you the fastest CPU, it only offers mobile graphics performance. There is no good reason why its internals, especially the drive bay are not user-accessible. While having a gorgeous display, why for all its expensiveness does it not offer any kind of video-in? If it had the ability to accept HDMI or DisplayPort input and display them in a special application window, that would be just great.
Especially, if Apple does not focus on the desktop, why are they so reluctant to sell a more traditional desktop machine? Where the user can change the hardware, if Apple cannot be bothered to do it?
All of this just adds up - and while power users in the pre-can age had at least an expensive but powerful alternative, this does not longer exist. And the other choices also get more and more limited. So it should not come as a surprise, when even the most faithful supporters get frustrated.