I think it's important to distinguish two cases. If mainly one app is the storage client, then you usually have the schema in the app, no problem with schemales

I think it's important to distinguish two cases. If mainly one app is the storage client, then you usually have the schema in the app, no problem with schemaless (most early phase startups). If you have many different server apps accessing the database, then everyone has a different view on the schema which leads to high coordination overhead.