The levels of canon is something that gets cited alot and imo tends to be misunderstood.
In practice, what it meant was lower levels of canon (such as books) were only canon if not contradicted by higher levels of canon (such as movies). This was mostly intended to offer a definitive ruling in the case of minor inconsistencies, but when something like TCW or The Force Unleashed is released, it means huge chunks of the canon, like multiple novel and comic series, become non canon over night.
If there were ever a Lucas sequel trilogy, it would never have respected the original EU. The levels of canon as they existed specifically allowed Lucas to invalidate as much of the canon as he liked.
It's funny how much people whine about Disney ruining the EU. It was never really canon. Lucas pretty much just gave fans permission to pretend it was if they wanted to. Disney has done more to make EU stuff canon than Lucas ever did, or would. ---