Really? The latter was immediately useful to lots of people which is motivating, and it had a nice smooth learning curve (html -> js -> php -> databases -> apps -> backend). Learning HTML is the first step to learning how to make full blown apps. Making a browser at 17 is like trying to climb Everest as your first hike. The expected outcome is burnout and demotivating failure. At best you'll learn some C++ or Rust.

17 is an interesting age. There are way too many comments here saying things like, 17 year olds should just do whatever seems interesting or bum around the world or focus on getting into university. But historically most kids were expected to be productive adults at 16 or 18. 17 is about the right time to be thinking seriously about what kind of work you'll do, how you'll make a living. University won't help and will just delay this decision.