This can be done easily in magento1 with the saveAttribute() -method of Mage_Eav_Model_Entity_Abstract . For example, if you only need to save the is_active -flag for a category, you can do:
$data = new Varien_Object();
$data->setEntityId($categoryId);
$data->setIsActive(1);
Mage::getSingleton('catalog/category')
->getResource()
->saveAttribute($data, 'is_active');
How can i do it in magento2 without using CategoryRepositoryInterface, only update one attribute?