Ask HN: Midlife crisis, which direction to go with?

I am in my late 30s, European, with kids, can't say I am a successful engineer at this age. Most of my life I did CRUD/backend services initially Python, later Go.

As I get older, I feel urgency to be an expert in area and go deeper, but I am still storing/pulling data from DB, transforming and presenting through REST/gRPC APIs.

Ideally, I would love to have a single area to which I can dedicate rest of my professional career, be it ML, ML Ops, Data engineering, Infra guy (AWS, Azure or GCP), maybe a security?

Any recommendations?