[Guthur]

This, completely.

Data modelling is the skill that is missing the most throughout the process. As you say that's developing a business domain model and mapping that to an appropriate persistence model. Both layers are important and quite often non trivial.

Working with a BA or technical product owner can help a lot in business domain and if you can use as much immutability as possible with a relational model you'll be in a reasonable position for quality development.