I've been on both Oasis and Allure and there are no wrinkles with the ports that I can see. Getting off these ships, and returning to them, is actually speedier than on smaller ships. Remember that the ports they visit have established special processes for handling the passenger loading. If the port can't handle it, these ships do not go there.
It is an excellent point about those who write bad reviews likely going on their cruises with champagne expectations but on a lite beer budget.