n'est pas très facile d'utiliser une base de données NoSQL (comme Couchbase, MongoDB, Cassandra, etc.) comme principal moyen de
stockage.

Flask is a "microframework", it doesn't include database integrations nor many of the things that come by default in Django.

This simplicity and flexibility allow doing things like using NoSQL databases as the main data storage system.

As it is very simple, it's relatively intuitive to learn, although the documentation gets somewhat technical at some points.