How easy do you find resources that can help a developer transition from intermediate to senior level?

I have noticed that there are infinite resources to get you started as a beginner, but rare ones that define advanced topics that can help you level up and reach a senior level.

There is some sort of unwritten agreement that you have to learn advanced topics the hard way through your work experience, but some developers are not lucky enough to be subjected to the right challenges that might help them grow. How do you educate yourself?