Is it me or did they just recreate Mongodb Shard feature? But now they have to maintain it. They would of been better off going Mongodb or another document data

Is it me or did they just recreate Mongodb Shard feature? But now they have to maintain it. They would of been better off going Mongodb or another document database. Then you wouldn't have to worry about scheme changes. Since your scheme lives there n your data model. You could just map changed fields. They should of just used a tenant based design. If a customer was hindering performance on neighboring tenants. They could just migrate them over to their own large server.