In my experience, ETL tools like SAP Data Services are often used for uploading data to SAP Marketing On-Premises, but do they still relevant for cloud version?
I guess not so much. Technically we still can use ETL but main point of using such tools are missing. Even if we extract data in bulk, at the end of the day we upload them in small batches via oData services.
PS
Good blog post SAP’s Data Integration Solutions in the Cloud