A positive thing to let you experience the consequences of your actions. You are ignoring the fact that the game explicitly tells you when this happens, giving you the choice to continue if you like or reload a previous save if you don’t. It’s actually more forgiving than dying in most RPGs, which would force you to reload from a previous save.
Couldn’t you just kill primary quest givers and be locked out of the game?
Yes. Many people view that as a positive thing.
A positive thing to be able to accidentally not be able to progress in the story?
A positive thing to let you experience the consequences of your actions. You are ignoring the fact that the game explicitly tells you when this happens, giving you the choice to continue if you like or reload a previous save if you don’t. It’s actually more forgiving than dying in most RPGs, which would force you to reload from a previous save.