I can only speak from personal experience, but I have noticed that I easily get excited to learn a shiny new tool or skill, but once I have basic familiarity with it, my eagerness dries up because all that was driving my desire to learn was the intrigue of an unknown experience. Times where I felt like I actually went deep (and it didn't require superhuman discipline to spend time on something I had lost interest in) were when I was working on a problem I was passionate about that required deep knowledge of a certain set of tools or skills. Then I had reason to keep pushing and along the way I realized I had become halfway decent at that tool/skill set.