For me, balancing feels forced (or contrived) the moment that micro-balanced rules have superseded the story I'd enjoy organically.
For example, I don't have a problem with a keen-eyed clever rogue who can sneak attack a zombie by knowing to blast its brains out.
But I do have a problem if only a rogue can "automatically" know or discover that zombie brain is the weak spot (especially if lacking zombie lore or prior experience).
And I do have a problem if an expert shotgun fighter can't deduce the same trick of blasting zombie brains just like the rogue did.
But I don't have a problem if it's a fast-moving zombie that dodges the fighter's shotgun blasts to the head, until that zombie is shot in the back of the head by the rogue who quietly snuck around from behind.
So the process matters. Fictional positioning matters. Simply stereotyping rogues as having a monopoly on finding the weak spots of all undead feels forced and contrived.
So sell me on the process(ess) of how rogues know how to sneak attack all undead in all scenarios regardless of morphology and why fire elementals should or should not have fire immunity and maybe I'll tell you "wow, that's a great story!" and issues of balance won't even come to mind.
Otherwise, I can't help but feel that a lame story or non-existent story is a slave to balance.
And I believe this view is somewhat supported by 5E previews stating that the story is the soul of D&D, and the rules will support the story.