To be fair, you don't get to be an expert at something by just reading about it. You become an expert by immersing yourself in it and knowing all the nuanced details of what you specialize in.

For example, I'm a AAA gamedev programmer. My specialty is the Unreal Engine. I know tons of little quirks about the engine that many of my coworkers don't - but that's because I've been using the engine for over a decade at this point.

I don't devote every waking moment to learning about Unreal - I used to spend a lot of free time researching it before I got hired, but now I leave gaming stuff at work to avoid burnout.

You don't need to like hyperfixate on something to become good at it. You just need to work on it for long enough - and if it's literally your job, you'll spend 40+ hours/week engrossed in it, for years.