Ifixit has a teardown of the 2014 Mac Mini, and the results aren't pretty.
Ifixit dropped the repairability score to 6 out of 10 from an excellent 8 for the prior generation.
Lower performance, more expensive RAM, reduced storage capacity, worse repairability. Apple's product management has done everything short of cancelling the Mini to kill it.
And there was no need. With the same form factor, they had plenty of room to use SODIMMs. They could have handled a quad-core i7 without thermal problems.
In short, the Mac Mini could have remained the bargain Mac of choice for budget-constrained power users. Probably some eagle-eyed beancounter realized Apple was leaving money on the table with the low-cost and flexible old model.
My advice: pick up a quad-core 2012 Mac Mini. More expandable, easier to repair and faster. The single Thunderbolt still supports plenty of connectivity — I have five Thunderbolt devices hanging off mine — that the quad-core can use productively.
Comments welcome, of course. Why do you think Apple crippled the Mini?