You are right in the fact that for complex systems, it will always be quicker to use an off-the-shelf solution than making your own. However, for maintainabilit

You are right in the fact that for complex systems, it will always be quicker to use an off-the-shelf solution than making your own. However, for maintainability, the most important metric is the raw amount of code, followed by the engineers' abilities and the code's level of documentedness. So, if you can replicate what you need with a third of the code, you are already in a much better position (and can fix your own code quicker than a third party's!) than if you had to wait for the vendor/a poor guy reviewing your pull request.