You almost certainly still need to worry about migrations.
MongoDB can store data in a schemaless fashion, however, chances are your application has a data model (schema).
Sure, you can avoid migrations and just tack on more and more backwards compatibility for old data layouts. But performance suffers, and chances are that code quality and correctness suffer too.
From a certain perspective, adding backwards compatibility for old data layouts is a migration. A migration that gets run every the data is loaded instead of once during a classic db migration. This is inefficient in the long run.
You have to deal migrations maybe 1/20 the times than with SQL. Like no migrations for new tables, new db, and new columns. Column name changes can be handled on the application side or yes with a migration.
MongoDB can store data in a schemaless fashion, however, chances are your application has a data model (schema).
Sure, you can avoid migrations and just tack on more and more backwards compatibility for old data layouts. But performance suffers, and chances are that code quality and correctness suffer too.