Yes of course ORMS use relational systems order the hood, everyone knows that. Relational Databases are easy to use, but that's not the problem. The problem comes from interfaceing the two different systems together. That's the problem. ORMS allow you to remove boilerplate, such manually populating objects, or connection code or whatever and still access relational features. They don't force you to use PURE OO to access data. If you wanted that you'd use a object database... They've existed for years.

ORMS allow you to use those relational features(HQL, LINQ), except without the boilerplate of manually populating objects, connecting to the database or whatever...

Nearly every search you perform via orm, uses relational operations...