One way to become more curious: learn a new skill completely unlike what you currently can do.

For example, learning to play a musical instrument if you've never been particularly musically inclined.

When you struggle to learn something that is challenging in an entirely different dimension, you learn to sense a dimension that was previously invisible to you.

Suddenly, you can see in 3D what previously you saw in 2D.

Curiosity is about being able to discern and discover gradations and dimensions that were previously invisible to you.

It takes practice.