Yahoo didn't have their own search technology, until acquisition of Inktomi in 2003 (they used Inktomi to serve their results prior to using Google, whom they used until ~2004).

Correct way to put it is "they didn't hire enough good programmers to build a search engine". A web search engine isn't something bad programmers can build. They acquired a great search engine (the algorithms were, IMO, better than Google's and more immune to gaming, they were a first distributed search engine paving the way for Google's "cluster of commodity hardware" architecture [1]), but it came too late.

[1] See http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.83.... for what I mean by "paved the way". Their mistake was using Solaris on SPARC (appropriate choice in 1996) for a few years too long (Google started on Linux/x86 right away, Inktomi transitioned by the time of Yahoo's acquisition).