It’s not hard to “really understand Git”. If anything, it’s the opposite problem—Git’s implementation is conceptually simple enough that the only good mental model the end user could possibly have is the implementation model. Systems like Subversion or Perforce or Fossil probably have even more complicated implementations than Git, and largely that’s to support a dumbed-down mental model that doesn’t require learning how the tool actually works. With Git, you learn how it works and you’re set, more or less.