[barry-cotter]

> making time to review your notes frequently enough that the knowledge captured actually sticks.

Strictly inferior to a spaced repetition system.

> Zettlekasten is a system layered on top of that and basically serves as a database for things you already know.

Things you already understand. If you already knew it in a deep sense it would be redundant. In reality zettelkasten enable you to think better by giving you a lightweight prosthetic expansion to working memory. You can get the same benefits by elaborative expansion but writing a ton of loosely related notecards is a lot less demanding than writing an article or book.