The "don't build your own" advice has a more specific piece of wisdom embedded. When you build and use a non-trivial piece of software, you also create a large

The "don't build your own" advice has a more specific piece of wisdom embedded. When you build and use a non-trivial piece of software, you also create a large body of non-trivial design and reliability issues, which will take you many iterations and possibly rewrites to get right. Mature software has generally had time to address those issues, and what isn't addressed is better understood by the users and implementors. When you roll you own, you have to ask: compared to the thing I'm replacing, do I understand the problem domain well enough to anticipate the issues?