To me, schema-less simply means that you don't need to maintain the data structure in a separate schema definition. It doesn't mean that your data doesn't have a structure - the structure is in your data, query and indexes, it's just easier to change without that extra "schema" definition.
It's not easier to change. When you have a schema-less database you don't change the schema, you add a new one for new data. Any data with an old schema continues to have it. So at any time you have up to n schemas simultaneously in your database if you changed it n times.
