Fusion originated with Miles Davis's "Bitches Brew" album. Pat Metheny, Larry Coryell and John Mclaughlin are probably the avatars of fusion jazz, but there are many many other practitioners of the genre, including Martin, Medeski and Wood, Bird Songs of the Mesozoic and the "downtown sound" of Bill Laswell and John Zorn.There are very interesting ideas that go on with fusion but the idea is to break away from the chains of mainstream or bebop jazz. As Miles Davis famously put it, "Don't play that bebop s*** !" Goodness, such vulgarity! But those are the emotions that came from fusion.
Fusion, like free jazz, attempts to reinvigorate a genre which was becoming fossilized and something like classical music. Don't get me wrong, I love mainstream jazz. I grew up with mainstream jazz. I also love classical music, but I feel that Monk, Bach and Stravinsky would have been appalled by the rigidity that jazz and classical music have taken.
Fusion was an attempt to break the rapidly rising walls that defined what jazz was. Walls that Wynton Marsalis has successfully rebuilt and maintained at the Lincoln Center. I have enormous respect for Marsalis, but I feel that his attempt to elevate and enervate jazz in the style that classical music has been elevated and enervated is a mistake.
In a way, fusion jazz came out of envy. Miles Davis was amazed at how much lesser musicians could be making so much money playing rock and he would be opening for the same musicians at such low wages.
But it became bigger than envy as some great artists led the way, other artists continued to build on the work that was being done. There are a lot of fusion guitar players who are terrible. I am truly sorry that you have been forced to listen to them. But listen to people that have come out of fusion jazz, such as John Scofield and Mike Stern and even Jim Hall and his protege Bill Frisell and tell me if you don't think that fusion has led to some amazing things over the years.
Miles-Davis Montreux 1986: