No 3rd-party dependencies
The framework itself doesn't have any 3rd-party dependencies. Our plugins do -- but we don't force you to use the same libraries we do.
For example, we are strong advocates for Dependency Injection and we really like PHP-DI, but you are free to build your plugins using either no dependency injection at all or using a different container. Whenever the framework references dependency injection, it simply assumes that it's been passed on a PSR-11-compatible container (which should be most, if not all, popular containers) and it always provides a fallback in case no container is used at all.
That being said, the framework does have internal dependencies. It is possible to build a plugin using only the Bootstrapper Module. If you need the Helpers Module, it will auto-install the Bootstrapper Module as well when using Composer since that is listed as a dependency. Similarly, the Foundations Module depends on both the Bootstrapper and the Helpers modules, and so on.
There is an exception though. The Settings Module does NOT depend on the Core Module as it is technically an extension to the Utilities Module. As the WooCommerce Module depends on the Settings one, it doesn't require the Core module either.