Comment by fragmede

Once you reach a certain level it becomes less about the stack itself and more about the bigger picture. What problems for the customer you're solving, what's the UX. If the stack there for historical reasons then just pick up that stack. Business don't generally care about how you solve their problem, they just want it solved. If you have to pick up a new stack to do it, then so be it. Is there a demand for that? Businesses still have, and will always have problems they need bespoke software written to solve. Choose whichever you want, you'll be valued either way. Specializing in one field limits the breadth of what you can do but the depth makes you more valuable, just in a different way.