Have you tried using external speakers? I think that should help with sounding more like, well, an accordion recorded fairly well. Just not from the player's vantage point. In my estimate, the audience will typically experience the least difference/downsides to digital accordions, so it falls to the performer to develop a rapport with the instrument and setup. Fun in playing for your own enjoyment and carrying a performance are not independent, but you can focus separately to some degree explicitly on making the latter work out (and figure out what part of working on that may be fun to yourself). Which is what distinguishes professionals from amateurs. Personally, I am just invested in being an amateur, making things work for my own gratification rather than that of others.