Get all enabled viewmodes of a entity/bundle
What @googletorp said is correct. But there is a concept of "enabled" view modes, just not like you're apparently expecting.

Enabled view modes are view displays. Enabling a view mode for a given bundle creates a view display which then stores the formatter configuration.

Same for form modes and form displays.

And I think \Drupal\Core\Entity\EntityDisplayRepository::getViewModeOptionsByBundle() will kind of give you what you're looking for. The view modes for which the given bundle has a view display.