MongoDB is a versatile nosql database that is great for web apps, dapps blockchain decentralized apps, even mobile apps. In 2022, MongoDB skills are still important relevant for data scientists.
The document model of MongoDB is flexible enough to be used to store all kinds of data. See official illustration below
It can be used for transactional data, search, mobile, analytics, data lakes, and can be used to model key-value store, geospatial data, relational, object, even graph!
"MongoDB is document oriented open source database which allows you to store JSON documents" - Johns Hopkins
MongoDB is a modern database services like firebase, neo4j, redis, HBase, Apache Cassandra, GraphQl