There are differences between languages here:
Yes, the plural form in English is "fruits", but that is only used when you want to stress they're different "types of fruit".
In Portuguese, though, you do "one, two, three frutas". Each "fruta" is a unit, just like "one, two, three oranges".
PS: of course you can still use the singular version in Portuguese sometimes when referring to a general thing, such as in "ele gosta de banana(s)", "ele gosta de fruta(s)".
your are misguided.
fruit and fruits are both plural forms of fruit dependent on its usage as countable or uncountable.
the Portuguese says "fruits" therefore the English should reflect the plural form. even the damn verb is plural so how do you rationalize "são" as "is"?
if there is more than one kind of fruit, the plural form "fruits" indicates with certainty that there is more than one kind of fruit. regardless of prevalence, the misguided use of "fruit" as the only plural form of the word is wrong.