Migrating content into AEM is nobody's idea if fun. Creating experiences and authoring content in the powerful AEM authoring experience is great, but identifying, classifying and mapping legacy content? Not so much. AEM's repository structure contributes to this challenge. AEM being based on the Java Content Repository (JCR) offers a massively more flexible content taxonomy than relational-based repositories, however, paraphrasing Uncle Ben, "with great flexibility, comes great mapping efforts". Web content generally doesn't deal with massive volumes of content, if your web CMS is the system is record for large amounts of structured content, you should have a discussion about what is the most appropriate system of record. The combination is the complex structure and relatively small volume makes traditional ETL tools such as Pentaho, Kapow or Apache Nifi a poor fit for migrating content to AEM as they are designed for high volume, predictable data.