I have noticed a bit of a correlation between polyploid fruit and vegetables, and general blandness.
Tetraploid potatoes are bland, diploid potatoes taste better. Triploid watermelons, even the high sugar ones, taste bland, diploid varieties taste better. Tetraploid tomatoes lack any noticeable taste. The very few triploid apples I have eaten were pretty insipid. And so on.
Is there anything to this, or is it just by chance?
I cannot say much about vegetables and watermelons, but definitely would not agree about apples. A lot of triploid apple varieties taste great, for example, Blenheim Orange, Claygate Pearmain, Gravenstein, Jonagold, Karmijn de Sonnaville, Mutsu, Orleans Reinette, Spigold, and many others.
I have a Jonagold apple that it Triploid. Tastes great.
Triploid watermelons get a bad rap in general. To me their issues are more about lack of size and being too dense in texture, not about taste.
Doesn’t play out with bananas.
Virtually all cultivated vegetables and fruits are allopolyploids. For a couple of examples, look up Okra and Rutabaga. Diploid tomato is actually an allopolyploid from a chromosome doubling event about 60 million years ago. Carya (hickory) is an allopolyploid for all the species from a doubling event about 70 million years ago and there are some current species such as mockernut that are tetraploid from a second chromosome doubling event about 6 million years ago.
So to answer your question, there is no direct correlation between ploidy level and taste.