Actually, in my day job, I do Analytics, SEM, SEO and the rest. Ironic, I know!
Broadly speaking, Facebook generates a lot of activity but little productivity compared to other Social channels. It's very well designed to keep its visitors nestled in its garden, thus building traffic for Facebook. Keeping the clickstream data from you and your site, not helping your SEO and rankings. It also actively discriminates its feed so you're forced to pay-to-play to get any traction.
It also, by design, encourages low-involvement activities, such as Likes or other interactions that don't result in anything actionable. Clicktavism is the term when applied to anything political done on Facebook. They hype Content Farming producers, low-quality, clickbait type stories.
Facebook does an admirable job of aggregating, then placating low-information, low-commitment, low-conversion audiences. Swell if you're aiming for vague, low ROI branding campaigns you want to tend to after all your other digital marketing ducks are in a row, but is a lousy primary use of your time, resources and spending. And it can become a huge time sink, distracting you from more crucial online marketing tasks requiring your attention.
Even worse, their customer support – and as a (potential) advertiser, you are their customer – is abysmal. Laughably so. They simply won't respond to anyone placing ads until you commit to a FB campaign involving thousands.
Use Facebook with this in mind. Make Facebook work for you, not for Zuckerberg. Third or fourth in your arsenal.
TL;DR: Facebook is not only a lousy deal for users' privacy, they are an even worse deal for advertisers trying to use it.