I think this is slightly reductive. The majority of your business logic, I agree, should reside in application code, but lightweight business logic in the form

I think this is slightly reductive. The majority of your business logic, I agree, should reside in application code, but lightweight business logic in the form of database constraints are powerful at disallowing bad data. For example, you may have a rental booking application that shouldn't have overlapping date ranges. The database can give you this guarantee out of the box and will work for ALL clients and applications.