All of those qualities are related to mixing and production. If the ambience or 3D is bad in the original mix, "mastering" can't and won't fix it.
The typical tools in a mastering studio are equalizers that can have their settings recorded and easily re-set, precision gain controls, again with repeatable settings, and a battery of dynamics processors, also resettable. The material that is being worked with is already mixed down to stereo. The need for repeatability in settings is very important when cutting a lacquer, because they'll have to cut several, but also useful for a digital master in case any re-release or re-mastering is possible in the future.
What I think is "well mastered" might be very different from what someone else things. The mastering engineer might define "well mastered" as a job on which he made his client happy enough to come back. A producer might define it as achieving his vision. An audiophile might define it as dynamic, clean, or the qualities mentioned above, not that they are related to the actual process of mastering.
