How often did you change the python/go compiler, how about an apache module? :)

edit: Point being every day you use a lot (i would say majority) of software which most probably it would be very hard for anyone to "change" and yet this seems to work. There's no point in making a decision to use some software by thinking "am i personally able to understand it's codebase". By this logic there is very little software one person should use, no one is able to know everything.

Let the experts (in that particular software) work on it, while you contribute to the things where you are an expert, everybody wins.

I remember an article here not long ago about the distinction between an expert and a smart person, interesting read.