Flashcards are an often-mentioned tool for memorizing information. On one side is a prompt, usually in the form of images or questions. When you study with flashcards, you look at the prompt and try to recall the answer, which is on the another side of the card. So if you are studying organ names, you may have some pictures on one side and the corresponding names on the other. You then review the cards one by one.
But this format has the inherent problem of disconnectedness. The cards are often made and studied independent of each other. There is no or little structure unifying a set of flashcards. Constrast this to a text: an anatomical text, for instance, may organizes its context by organization, function, or the level of structures. It may talk about the brain by regions, by how certain events occur, or by looking into different levels. In any case, the information is interconnected—there is a flow guiding them.
This structure is lost when we put them into flashcards, where each piece of information becomes a standalone fact. You end up with hundreds cards with arbitrary pieces of information you have to memorize by rote. A lot of connections are discarded, and this pushes us to the rotest end of learning.
This problem is exacerbated by the common ways flashcards are used. For instance, the cards you can answer correctly are often put into a different pile from those you cannot answer correctly. This means the continguity of cards is not preserved. Cards with related content can be separated and thrown around. The piece of information becomes isolated, and you are not going to remember it well without adequate associations to other things.
As such, flashcards trim away associations between pieces of information that are essential for memory. They can still have some niche use, but they are still very limited in most learning contexts.