May peace be with you,
The tradition of memorising scripture is an old tradition which from a Quranic perspective, seems to predate it. From the Quran, even the Jews were entrusted to guard / protect (hafiz) their scriptures which also implies the ability to commit to memory for the purpose of recall and learning.
005:44 (part)
"...with what they were entrusted / commit to one's keeping or memory (Arabic: us'tuhfizu *) of the Book of God..."
* Istahfaza (verb) - to commit to one's safe keeping / or memory for preservation / guardianship
In my humble view, any action which at its heart has the intention of seeking God's grace (or an avenue to him - 'wasilah' 5:35) is arguably within the realms of reward (and God knows best).
Of course one should attempt to understand the Quran’s guidance and implement it in their lives. However, it is also important to appreciate that at times, deep learning can come later in one's life whereas the ability to memorise is committed in the earlier formative years as a child, when the faculty to memorise is at its most acute.
I hope that helps, God willing.
Joseph.