To be fair, there's a REASON we use libraries that contain features we don't necessarily use.
Fair? How about "to be even modestly rational"?
I don't know why these "so-called experts" aren't tapping out their own silicon, then writing their own assemblers, compilers, OSes, network stacks, HTTP servers, TLS implementations, DBMSes, web browers... Why, those things are just chock full of features most applications don't need.
Yes, there's much to be said against bloated, poorly-written libraries. Anyone who pays the slightest attention to information security understands the problem of a broad attack surface. But "write everything yourself" is not a good answer.