The decline started way back when they stopped letting you find mp3's and mp4's of movies and albums. I get that copyright infringement is bad and all, but their engine was fully capable of you typing a obscure phrase, and being able to get web results. Somewhere behind all the filters a lot of powerful searching capabilities just died.

If I had unlimited money, I'd make a fresh search engine, zero filtering to start outside of blatant spam sites, and go from there. Focus on making results be powerful.