It drills in pretty far, but there are granular components that don't show. Granted, it's freeware, you can only expect so much and at with minimal support.
BuiltWith has a large number of technology signatures but many of them are outdated and they don't use technographics. Allora (Datanyze, SimilarTech etc) provide much cleaner data with less false positive results.
Datanyze (tech tracking) = VERY INTERESTING
Datanyze is quite possibly BuiltWith's most direct competitor. Their specialty is providing data on the technologies being used by millions of websites. They can tell you things like who started or stopped using a technology today, among other data points that provide actionable insights.