I think the key is balance. The people I’ve worked with who are the most effective and successful are really good at one or a short list of things, but have their hands in many other things.
And often they’re really good at the one thing because they have their hands in many things.
Cultivating a breadth of knowledge often isn’t just being mediocre in a bunch of subjects, but about broadening one’s awareness to potential connections and opportunities.
If you can’t go deep on anything, that shallow knowledge may not get you very far.
But if you can go deep on X subject with enough surface level knowledge of a variety of potentially related topics, you’ll be able to accomplish far more interesting things than someone with equivalent but exclusive knowledge of X.