Let me caveat this response by saying that I've never had to pass a rigorous technical interview process [A timed written test regarding Fundamental Controls Engineering is the toughest I've had to beat].
The way I become better at specific tech (languages, frameworks, concepts, etc.) is to dream up a project, design and plan it, then build it.
Your imaginary project doesn't need to be very elaborate or accomplish anything major. Just going through the motions of building something using your targeted learning topic will be much more educating than doing tutorials, In My Opinion!
I must have completed 20 or 30 tutorials with Node.js before I gave up, and just built a tiny command line app, learning about what I needed ONLY when the application needed it.
The difference is a tutorial tells you the next step, creating the illusion that you understand something. When you create your own app, (no matter how simple) you can't do the next step unless you really know how to do it.
Also, your own projects can serve as a sort of skill level proof if you get to reference them, or even better demo them during your interviews.
Best of luck to you on your self-improvement journey!