I also like being able to get a terminal window to fiddle with the guts when I want it. Some tasks are better suited for that interface, and some powerful tools are only available there.
During those better days, Apple fully embraced the UNIX nature of their OS, without compromising the usability of their GUI layer. They got Mac OS X certified by The Open Group. They started opensource.apple.com and distributed enough of the OS's guts that you could actually get a full Darwin OS up and running entirely from source, even if the result wasn't super useful. They gave out a full suite of developer tools free of charge that you could use to build powerful apps for the system, and were in fact the exact same tools that Apple used.
Then iOS came. No more open source, except the absolute bare minimum they're required to distribute for open source licenses. (Their open source archive for iOS 9.0 contains a whole six packages, of which five are various parts of WebKit.) No more visibility into anything. Everything runs in a sandbox that you can't bypass by any means except finding a security vulnerability. The developer tools are still free, but if you want to actually use them to ship anything, or even run anything on real hardware locally, you have to pay and agree to their terms. (The "run anything on real hardware locally" bit has changed with Xcode 7, which is what f.lux was briefly taking advantage of, but this is new as of just a couple of months ago.) Apple suddenly wants to play gatekeeper to everything; if you want to ship apps to your customers, you have to first let Apple review and approve it, and they'll reject you if you don't follow their rules.
The Mac retains much of what was great about it before, but it's slowly drifting the same way.