For the time I worked there the metric was engagement (with occasional Cares about Facebook intermissions).
One look at newsfeed tells you it’s ad revenue now. Quality has nothing to do with it unless you define quality as clickbait.
In fact, citation needed on “high correlation” unless you take a meta press release which are notoriously misleading. Like 3% of the platform being news
I'd say it's a huge concern due to its strong correlation with increased usage and thus ad revenue.