Author here, I have 4, soon to be 5 small kids, a full time job, church responsibilities, etc. This exploring and tinkering and learning doesn't have to take up a ton of time. 30 minutes a day can make a huge difference. I get quite a bit done while sitting with my kids while they fall asleep each night.

I also play tabletop and board games, watch TV with my wife each night, and even play Mario kart with my kids. There's plenty of time.

That said, my advice was primarily targeting recent graduates or young developers who are looking for a job. That implies they have plenty of time and are trying to put the bulk of it towards finding a job. If I were in that position, I'd treat building my resume and finding a job _as_ my full time job.