I was doing some research a year ago or so on which Mac Mini to buy - currently using one from 2006 or so, which can't handle https sites mostly, but otherwise is great.
Everything I read said to get the 2012 model, not the 2014 one, which was slower, less memory, less everything - way worse. So the last one before this new one definitely did get a lot worse.
I have a 2006 Mac Mini that refuses to die. I ended up putting Windows 7 on it and giving it to my mom. She still uses it as a secondary computer when she is tutoring.
Everything I read said to get the 2012 model, not the 2014 one, which was slower, less memory, less everything - way worse. So the last one before this new one definitely did get a lot worse.