Well, it won’t fix the “one correct way” problem. But it does do the following:
1) Makes explicit the idea that there is an elegant and appropriate use of language, and puts to rest the canard that “descriptivists are too permissive, don’t give a damn about ‘good’ language.” (I don’t think there is a descriptivist or linguist on the planet who doesn’t also have a problem with bad writing or speech, although ideas on what constitutes what is bad may vary.)
2) Shifts focus onto how we determine what is elegant and appropriate rather than on whether we should make the determination at all. It puts pressure on those prescribing how language should be used to justify their prescriptions. (Which in some cases may indeed be justifiable.)
3) Recognizes that no matter how linguists go about the business of their discipline, most people turn to linguistic resources to help them determine what is the best way to use language. People want normative rules, and there should be a place for them.
And when it comes to the “one correct way” problem, most people don’t have a problem with that in general. 99.9% of people will concede that language changes and there are different registers that are appropriate for different contexts. It’s the specific cases that bug them, and by pressuring them to justify their prescriptions in individual cases, the “one correct way” problem may fall by the wayside.