If you believe that JPII was canonized by a true pope and therefore an infallible declaration, then you can not disagree with it.
You missed my point.
Canonization means that JPII is in heaven. I cannot hold that he is not in heaven. In that sense, I cannot “disagree” with his canonization.
I can still think that he should not have been canonized, on the grounds that he was not a great Pope. In that sense, I can “disagree” with his canonization.