1) Google focuses more on commercial sites, especially branded sites, than research or personal sites.
2) Sturgeon's law (90% of everything is garbage) and a much bigger world wide web means that there's a lot more garbage indexed, and returned, by Google searches.
I remember that I'd try a search phrase, and I'd be taken to some Web 1.2 site with black text on a grey background; some university professor or doctor would have written a really interesting article and linked to other sites or research. Now I get some reputable site selling stuff, or a bunch of shitty link farms offering me god-awful "reviews", or awful awful blogs.
I remember when search terms would return less than a gajillion hits; you could tell by the extra 'o' in Goooogle how many hits you'd got. When was the last time GoogleWhacking was possible? A result of "zero hits" is important. It doesn't mean the search failed and that Google should feel free to substitute words and try different stemming and remove the quotes. "Zero hits" information for me.
I strongly agree that I'm an edge case, and that Google is great for most people.