A little while back, I got a brand new 2014 model Mac Mini. Base model with the 1.4GHz Core i5, 4GB of RAM and a 500GB hard drive. It runs macOS 10.14.2 Mojave. Once everything was set up, I noticed that it was really unresponsive when trying to use elements of the user interface. If I clicked the Apple logo in the top left corner of the screen, it'd usually take at least a second to open, sometimes up to 10 seconds. Same thing with the Dock, the application would only start opening up to 10 seconds after clicking an icon. Selecting, moving and opening objects on the desktop is similarly slow and unresponsive. Right-click contextual menus take several seconds to open. The computer isn't slow running my applications. Google Chrome works well and is responsive, Brackets and Xcode are totally usable and rarely unresponsive, and video editing in DaVinci Resolve works much better than I expected. Exceptions to this are the built-in Apple applications, such as Safari and Mail, which are excruciatingly slow to use. It's just getting everything going and UI navigation that's the problem. It's bad enough that I don't want to go switching between applications or doing anything that requires clicking icons in the user interface. I recently reinstalled everything from scratch as I read somewhere that trying to copy files from another computer during setup (which I tried doing when I first got it) could result in a slow computer, and even though this new installation is a little bit faster and more responsive, it's still too unresponsive. I know it's got a mechanical hard drive and so opening programs won't be as fast as an SSD, but it's slower than I'd expect from a hard drive. It's also the slow and unresponsive user interface. I've got a Core 2 Duo MacBook from 2009 that runs macOS 10.11 El Capitan - it's perfectly responsive, as clicking user interface objects results in an immediate action. I have no idea what to do. Maybe it has something to do with running macOS Mojave on this hardware, maybe it's something else. Does anyone have any ideas?