I watched a little bit of it, but I think the lack of interest is just due to the fact that there isn't really a story around it at all? And the media coverage seems pretty lackluster.
America's Cup had it all, massive build up, piles of speculation around which team had the best technical solution, dynamics within teams i.e. different boat management schemes (two captains vs 1, different roles on diff boats), usual legal shots between teams, bragging rights and massive egos on the line. And all the media coverage to go with it, including the excellent technical analysis from Mozzy Sails, which really elevated the experience I think for anyone who was semi interested.
SailGP, they are all on one design boats so there's really nothing technical to get interested about. One design should make for good racing, and I think it does for the sailors, but for spectators, there is no story there, where are the rivalries? Its just a bunch of good sailors ripping around a course, with their mates, maybe some big $$ sponsors but really nothing on the line. Is there even any commentators? The wrap up videos are just a bunch of video cuts which give no context as to who is leading, who's losing, who has anything on the line. The whole series really just seems to lack any personality.
What you need is some commentating like this:
And technical analysis like this:
I think the fact that its unattainable for your everyman pretty much has nothing to do with it. Just take things like F1 for example.