3 days ago I used to wait for a transaction around 12hours. And the transaction fee was average. But I think the network was overloaded.
This is not overloaded, this is just a queue waiting for miners to transport and process the transactions we are doing.
If you know that your fees are average then don't expect that it will be confirmed quickly. And OP is right that the network isn't overloaded, looking at the number of unconfirmed transactions it's amazing that it's becoming low these days.
https://www.blockchain.com/btc/unconfirmed-transactionsBefore it's around tens of thousands of unconfirmed transactions that makes each transactions to be unconfirmed for a long time.