I think it's accessible to most musicians, but if you try to play Mahavishnu for someone that's not really into music, it just sounds like chaos and noise. It's the same with free jazz, people that aren't into jazz are going to just hear noise, whereas (even if we don't like it) musicians can hear and appreciate what's going on.Contrary to the vibe I'm getting with your write up, I find Fusion to be the most accessible style of jazz, at least with post-bop styles. Just because it is a fusion of rock, so there's a lot of familiarity. As a rocker myself, I can really get behind a lot of fusion.
Even they're labelled as prog rock, there are many King Crimson songs that are straight up jazz/rock fusion. Especially their modern (post 1982) stuff, but even going back to their very first song on their very first album, 21st Century Schizoid Man.
Mahavishnu Orchestra is another popular example of fusion, more jazz than rock but still accessible to rock fans.
I've even met several musicians who think of fusion as elevator music or as being too complicated to enjoy, that's the only reason I put the disclaimer