One of the features of the Khawaarij was their tremendous ability to memorise. This is a mistake made in a lot of the Arab countries, even by mashaayikh, that you just keep memorising. This is problematic in 2 ways:
You memorise and don’t understand what you’re memorising.
You don’t implement what you’re memorising.
So we say memorise by all means, especially the Qur’an and Hadith, but do so with understanding and implementation.
Don’t be impressed when you hear someone’s memorised so much until you can see it has been implemented.
When the mashaayikh say to memorise Hadith and so on and due to this you’ll become this or that, they are saying this to people, they presume, who have clean hearts so the ilm is going into a safe place. The reality is most of us don’t have clean hearts.