But due to restrictions on one platform, Firefox can’t provide the functionality that the users want.

With all due respect, I don’t think you understand. There is no restriction on language translation on iPhone. Firefox merely doesn’t support built-in language translation. It might have been easier for them if Apple permitted add-ons on iPhone, but it definitely does not prevent language translation. Chrome and Edge have built language translation into their apps for iPhone to facilitate this. Firefox could do the same, but have chosen not to.