Why do you say that? It doesn't signify a lack of understanding of scripture.
You addressed your comment to “all” and so I feel justified in replying. So....
In Matt. 16:19 Jesus said he would give the keys to Peter sometime in the future, “I will give..” Not “I am giving.,..”. Peter getting the keys was a future event.
In Act 10:15 Peter in vision is told to stop calling defiled “the things God has (the decision has been made and is in effect) cleansed.”
There is a sequence of time here. Peter is not opening up a new opportunity or making any decision for Cornelius and those like him, that has already been made in heaven.
What role then does Peter have with the “keys”? He is one through whom heavens decision is made, Cornelius is sent to him, to Peter.
At Acts 15:6-11 Peters shows how he had a key as he says it was, “through my mouth” that the message was given that people of nations would be treated without distinction and without having the old Law imposed on them.
Peters used of the keys then was as one announcing heaven's decision not making decisions on any of these matters himself and when he had done so he had used the keys. Others like Paul would take up the message but Peter had a privilege just as John the baptizer did.
Peter used the keys, there are no more for Peter use.