Earlier quoted context omitted.
In this sense, trivially, every tool is a "professional" tool, since if you just rote-memorize every aspect of it you know how to do everything it can do. The problem with git is the lack of coherence in its default UI. Multiple ways to accomplish the same task, git commands which perform incredibly different functions depending on (invisible) context, inability to decide whether commands or flags should act as the h…
No, trivially, there can be tools that you know inside out which still present roadblocks to perfectly ordinary tasks and be a bad fit for the domain they operate in. Visual SourceSafe springs to mind here... Git, by comparison, is very flexible and allows you to do an awful lot, when you've learned it. You can learn SourceSafe inside out and still have it be a total pain in the arse.
Nothing in that interface is designed to aid in learning. Nothing in it is designed so that mastering one task provides discoverability or intuitability of how to perform another task. It is a complex mess of inconsistencies, discontinuities and obscurities which point more to a lack of design or even of someone with authority to perform design than to anything else. It can only be "mastered" through rote memorization, and bears no necessary or useful relationship to the underlying data models and structures whatsoever.