Standard saccharomyces will ferment all the simple sugars, unless interrupted. Some fruit don’t have much in the way of complex sugars (which are responsible for rounding out flavour), and some fruit just don’t have a pleasant flavour without sugar present. It’s also possible that there’s a Brett or other bug in there that ferments the less simple sugars and brings it down stupidly dry. I think plums are on the stupid dry list; I’ve had them in a sour beer and it was… crushingly tart.