Ask HN: How to grow as a software engineering generalist?

I am working as a software engineer at a tech startup in India where our tech stack is Django on the backend and Angular on the front-end. I have learnt enough of the two technologies to be able to do most tasks but would not consider myself an expert in either of these two technologies.

I am more interested in being a software engineering generalist than in being a Django or an Angular expert since I don't want to be doing web development all my life. My company is unlikely to expand its tech stack beyond these two in the near future and frankly, there isn't much in the way of technical mentorship being offered to me either. On the other hand, I've also been given a lot of managerial responsibilities. As a result, I am feeling that my technical growth has become restricted.

Should I be learning another language such as C++ or Haskell in order to grow myself? Will my experience at Django and Angular fetch me a job at a company that works primarily in C++ if my only experience in C++ was outside work in hobby projects?

For eg. Will Google ever consider me employable as a senior engineer with my 3-4 years work experience in Django and Angular? Or will Google treat me like a fresher?

PS: I have a bachelor's and master's in CS from a reputed university (IIT) in India and have been working at my current company for the past 3 years.