no, not true. a generic structure would be so generic that you lose the performance benefits, indexing, and integrity that the database offers.
for example, i have created a recommendation engine that takes in dynamic attributes from an organization, which are manipulated and weighted. for now in SQL they are individually entered as rows rather than structure, allow for an unlimited number of attributes... but it forces them to be "virtual" attributes, where the types are defined as metadata, and then functionality built around in code to enforce the functionality. the database doesn't
get to enforce that a string attribute is a string in this scenario.