IIRC they did deviate a little bit to avoid the worst of a thunderstorm. But the point remains, that plane was flying along a known route, never disabled any electronics or communication, was flying over waters that are far more commonly used traderoutes, it still took 2 years to locate the black boxes. Also one of the reasons the airfrance crash site was found so "quickly" was that it was a modern airbus with lots of light weight composite materials. The entire tail, which is huge, just floated. Thats a tad easier to locate than some seat cushions.  By contrast, the older 777 hardly uses any composites and of course, we barely have any idea where it went down.