I think it depends on how the culture is toxic. Amazon's culture seems to be "toxic" in a very specific way: that it selects for a very particular kind of person, with particular kinds of motivations - those who don't align with that are unhappy and leave quickly, those that are stay and perform very well.

I think there are ways Amazon could improve its culture, but apart from widening the potential pool of effective hires, I'm not sure it would benefit the company a huge amount. However I think Amazon is the exception to the rule, and in general I think toxic cultures are a significant hindrance to most companies.