What can Blueprint do that UE C++ can not?

Blueprint makes some scripting easier (in particular for non-programmers), expands c++ code and exposes functionality to artists and designers, but…is there more than this? And, most importantly, can Blueprint do something UE C++ can not?
I’m interested in knowing how UE can handle story management, like keeping the story state and offering to the player state-aware quests/interactions. Or maybe some debugging capabilities, like spotting narration deadends (like this: the player needs a key to go on, but the key is behind a door that now is closed). Is there some built-in mechanism in UE and more precisely in the Blueprint framework to avoid these problems, or is that something every developer should build on their own with the tools UE provides them?