It's been a long time since I worked at Google but when I did (10 yrs ago), the search system for the intranet was notoriously awful. Part of the reason was that PageRank tends not to work so well in places where things aren't heavily cross-linked, which is a hard place to get to if you search system already sucks.
I always found those complaints funny. Google's internal search was and is light years ahead of every other company's. Those complaints were probably coming from people who never worked at any other large company and were expecting internal search to be as good as web search despite the relatively tiny corpus.