[fallous]

I'd agree with your criticism of tool/new hotness as a bad metric for measuring leveling up. It's too easy to get the dopamine hit from novelty or being busy rather than putting in the real work that provides value.

We learn to solve the same problems better because we're exposed to the limitations of our initial naive understanding of those problems and the methods we choose, which may be sufficient in the first year, but over time that understanding becomes deeper and the methods become more elegant, reliable, and maintainable.

The wisdom and methodology improvements are necessary components of achieving 10 years of experience, but the 10 years of the same year approach literally is staying at the same level of understanding no matter the number of projects.