Content quality is the most generic, vague factor on the ranking factors list. However, high quality content has always been praised by Google as one of the most important ranking factors, many times:

“FACT: Having original and useful content and making your site search engine friendly is the best strategy for better ranking” source

Don’t mistake content quality for content lenght. More is not necessarily better. High quality content is content that matches user intent. It varies from one industry to another, and from query to query.