The way I see it is, if you don't expect to make the Barbarian's player lift weights or swing a real sword, you shouldn't expect a Wizard's player to always have the right answer, or the Bard's player to always know how to be charming.
Lots of people believe they are smart or witty or dashing. If you have a Charisma of 8, and you think you're God's gift to your preferred gender(s), you can roleplay as being as suave as you want to be- the dice will tell the tale- and if you succeed anyways, well, maybe you're a
Kavorka Man!
By the same token, maybe your fumbling, tongue-tied Bard with a 20 Charisma is just so plain adorkable that even the mean-hearted BBEG is like "daww, I can't stay mad at you!". Skill at oratory and public speaking =/= being charismatic- it sure helps, but that's being trained in Persuasion, not having high Charisma.
And if a supposedly smart or wise character keeps making bad decisions, well, some of the smartest people I know are morons, lol.
Sure, we all want to shower gifted roleplayers with accolades, but we can't let the game become a series of "persuade the DM" checks. This is what Inspiration is for, IMO. If the Barbarian waxes eloquently, award him Inspiration, and then let his player live with the choices he made. And never force someone to wear a dunce cap- they'll likely make their lives more painful without any help from you!