As I matured into the profession, I went through stages of dependency. In the beginning, I wanted to build everything myself because I was learning. In retrospect, this was a good choice because I was way too green to pick a dependency and at least I knew my own code was crap. Then, I reached a place where I wanted to stand on everyone's shoulders - I agreed that any code I had to write myself was code I had to maintain myself.
Lately, I see all the grey in between those two points. I'd sooner not try to reinvent React because that would take me an obscenely long time. But, for more trivial things like left-pad or escape-string-regex, I've discovered that it's cheaper to implement and maintain it myself than to go through all the steps to vet a new dependency.
There's a strange place in this industry where rolling your own solution is cheaper in the long run.