I think analyzers are really good for giving you an visual representation of what that particular instrument or track is doing but I certainly wouldn't do any EQ-ing based on what I saw.
You also have to be aware of whether it's the fundamental or a harmonic that needs to be treated or whether the overall timbre of the instrument is correct for a song. Sometimes just changing the instrument or the source i.e. DI or mic or mucking with compression can make a huge difference
For example with a bass guitar - I had this one bass guitar that just wouldn't play nice...beautifully recorded, good timbre and well played but after futzing with it in various ways it just didn't sit well so I tried a little distortion on the upper harmonics and Bob's Your Uncle, that was what was needed.
So I guess what I'm saying is use your ears, take the time to learn frequency ranges and how each effects individual instruments and you'll never need a spectrum analyzer. It's not hard, it just takes a little time