There are two reasons for thinking someone should not be canonized: 1) It was bad for the Church to do so; 2) One does not think it’s safe to say the person is in Heaven.
I don’t think it was a good idea to canonize Roncalli or Wojtyla, because I don’t think the Church should canonize Popes who were a disaster. Roncalli called the Council, and Wojtyla was totally, totally negligent when it came to the appointment of bishops. And there’s Assisi.
But the Church claims infallibility when it comes to canonizations. That means that I can think neither Pope should have been canonized, but NOT because I think they are in Hell!
That is if the canonizations are defined by a true pope.