In my experience, if you have the relational database model fully defined and correct then the rest of the application is pretty much designed. All the screens and elements you need are obvious.
If you can get your service boundaries and APIs fully defined and correct, then the relational database models (underpinning each of those services) just fall from the tree for you.
And then as you say the screens and elements are obvious.
I find if you start at the database model layer you much less likely to screw up the API design. The database model forces a bit of rigor that you can't get going the other direction.
But if you're building a system which is not a monolith, and instead is made of up of, say, 20 services, then putting good boxes around those services and defining the lines that connect them (the APIs) is an essential prereq to designing the databases that sit inside the boxes.
(Though really what's happening, as always, is you're doing it all in parallel, just with more emphasis on the higher level stuff).