Seems to me, every instrument has a limitation, but it becomes obvious when you substitute one instrument for another. You can't really get a piano to do the kinds of things you can do on guitar, and I think that's the essence of the problem with trying to get a harmonica to do accordion licks - or the other way around. Blues on the accordion IS limited if you focus on trying to get it do sound like something else. For me, G on a C box works for what I call up beat blues (Midnight Special, Sweet Home Chigaco genre), and D on a C box works on the down home, gritty stuff (Dust My Broom, Come Into My Kitchen genre). No instrument is good for everything all the time, but I think sometimes we limit ourselves to preconcieved notions too much. Just an opinion.
Steve