You've probably seen this quote a bunch of times now:
A human being should be able to change a diaper, plan an invasion, butcher a hog, conn a ship, design a building, write a sonnet, balance accounts, build a wall, set a bone, comfort the dying, take orders, give orders, cooperate, act alone, solve equations, analyse a new problem, pitch manure, program a computer, cook a tasty meal, fight efficiently, die gallantly. Specialization is for insects.
— Robert Heinlein
It's not that he's wrong, only that he's not describing the whole picture.
If any one of us is fantastic at differential equations but only okay at making Lobster Thermidor, that's why we have a society. On the other hand, if you only know how to do differential equations, but don't know how to maintain basic bodily hygiene, that's not great either.
There's nothing wrong with dedicating yourself to doing a couple of things deeply, completely, whole-heartedly, as long as you don't starve the rest of yourself to death in the process.
Specialization isn't for insects; it's how we as a species are able to move forward — by allowing the deep interests of a few become in time the province of many, and eventually all.
A better way to put it: Over-specialization is for insects.