It depends where your starting point is. Core bundles a lot of stuff together that was previously separate or just good practice. If you are familiar with MVC / WebAPI / EF / OWIN and already doing DI / Logging etc. then it's not much of a leap.
I feel "DI" in the context of .NET Core is often the IoC container you feel forced to use. DI is a pattern, but even trying to use the logger extension without the service provider is a pain.