We have sweet fruit... Also dragon fruit are another example of a fruit that doesn't sweeten that well here. At least the big red ones white or red fleshed. They taste like water... In Thailand they can be hyper sweet. I never said black sapote taste like persimmon. I said I heard They can be sweet like a ripe persimmon.
Dragon fruit in Thailand is notorious for being super bland. Again it has to do with cultivar chosen, not with the fruit itself. But a lot of people complain that dragon fruit is tasteless. (Read many past threads on this forum about dragon fruit.) And they come from many different countries. Same is true with marang, or practically any fruit. If you have a bad selection, and Ken Love obviously does, then it's not going to be the best tasting.
Right now i'm eating loss of mangosteens from my trees which are super sweet. Never really fully appreciated this fruit until now. The ones i had in Thailand were a lot less tasty. I think this has to do with depleted soils there and use of chemical fertilizers.