You cite a time when the algorithm failed. When I use Google Maps, a service that is constantly taking positional data from users, their speeds and extrapolating that to the current situation, I get there faster most of the time. In general, an algorithm, any algorithm, outperforms judgement. Sometimes it fails and Google Maps has failed me spectacularly in the past but it has more information than you about traffic conditions, real-time speeds, so its decisions will almost always be better than yours. Except when they aren't.