Sorry, I should have clarified "heavy" in terms of the level of OOP [1] insanity but yeah Symfony is very modular.
[1] e.g. "Symfony\Component\DependencyInjection\Loader\Configurator\ContainerConfigurator"
[1] e.g. "Symfony\Component\DependencyInjection\Loader\Configurator\ContainerConfigurator"
I would have to question how relevant a piece of core plumbing is to a regular user of the framework, as a regular user of the framework would likely never come across this class.
Also if you're working in the domain as a Symfony core developer, the idea of a ContainerConfigurator is not so insane, if you're developing a dependency injection container.