I have one niggle on schema-less. The fact is, the database probably shouldn't care about the shape/schema of the data in some cases. That's what application logic is for. If you want to support multiple payment gateways, do you
REALLY want to create a half dozen or more connected tables to store the transaction details? Oh, this table is for transactions from Paypal. This one is for Authorize.Net. Or add a Transactions table with the common bits as typed columns and a json field NVARCHAR(MAX)?
There are times to pragmatically make choices. Joins, and subqueries have costs, and they become more so at scale. In the end it's frustrating to have to debate/fight for a simpler solution because the lessons and positive points of the last decade were never learned.