I don't know what distinction you're trying to make about "canned" vs. other things. There are advantages and disadvantages of using libraries in any language.

I don't know what distinction you're trying to make about "canned" vs. other things. There are advantages and disadvantages of using libraries in any language. There are some aspects of C —e.g. the lack of garbage collection— that make it harder to reuse code compared to some languages. But it is definitely not against "C's spirit".