"Every perception is to some degree an act of creation, and every act of memory is to some degree an act of imagination."
-- Gerald Edelman, Second Nature: Brain Science and Human Knowledge
How important is long-term memory, anyway？2 How important is long-term memory, anyway？How important is long-term memory, anyway？Augmenting Long-term Memory2020-09-24Journal
There are two main reasons for this change, one a personal experience, the other based on evidence from cognitive science.
Let me begin with the personal experience.
Over the years, I've often helped people learn technical subjects such as quantum mechanics. Over time you come to see patterns in how people get stuck. One common pattern is that people think they're getting stuck on esoteric, complex issues. But when you dig down it turns out they're having a hard time with basic notation and terminology. It's difficult to understand quantum mechanics when you're unclear about every third word or piece of notation! Every sentence is a struggle.