Short answer: No, it doesn't.
Long answer, beginning with 'but': But translation is not the same as target text. Whether a bad target text is justified — or even required! — by a bad source text depends on the intended purpose of your translation, the so called skopos, and your arrangements with your client.
Suppose you're translating a love letter a certain mademoiselle has received from a certain mister. Mademoiselle pronounces weekend and basketball in a funky way, and mister can never get entrepreneur straight, or even au pair. In short, there is no hope of communication — without you.
Well, we're pretty much all sure that mademoiselle would very much like to receive a stunning pretty letter, be swept off her feet with butterflies and all, but if you turn mister into the next Abelard, will mademoiselle not, in the end, have become his Heloise under false pretences? Hmmm?
Also a court of law may need the information conveyed by the writer's or recorded speaker's idiolect, mannerisms, any twitchy behaviour, and even perhaps things such as dialect features, markers of a certain education or origin, all of which can have some kind of significance in some kind of case.
Similarly a publishing house could possibly (and had better) want to know the foreign manuscript for what it really is, not what it can be made into by a generous translator.
If your agreement provided for editing or transcreation, or at least your client has asked you to fixed some things as you go, then that's a different matter altogether. In case of doubt, ask. Don't presume.
And don't contribute to getting translation clients used to the thought — or sensation rather — that translation is supposed to bring nirvana to them as they read what was a poor source. Because translation is not about serotonin.
And don't teach lazy authors, publishers and others that a translator will carry the brunt of their workload, either.
Afterword. I really mean ask them. Spawning the nicest possible text for publication is not the only purpose of translation that exists. For information is a legitimate purpose and one which is frustrated by a translator who puts golden lacqueur on a worn truck.