Using a predetermined set of roles, events, artifacts and rules is like having a GPS that just gives you the directions without the map. If you get lost or you can’t make a turn or you miss it you are lost.
Being given a map with alternatives to get there provides not only options that work for you but provide a way of getting back on track when you get lost. In the complex world of software development it is even more likely you’ll need this ability.
Many people require a given set path. But have it include where you are and have it provide you with a reset option when you get lost. This is what Lean-based team Agile does. Scrum doesn’t even try because you are out of Scrum by this time. Scrum proponents just call this Scrumbut and go on to the next team. This doesn’t mean you can’t use Scrum, it just means that when you do Scrum you should do it within the context of Lean.