I definitely agree that digital literacy should include critical questioning of assumptions and platforms. It's vital we understand that parameters that define our social media experience and that shape or bias our search or networking.
One thing that's striking about young people is their willingness to get off Facebook or take up Instagram or divide their social networks across several platforms, and then change it all. It is those of us who are older who, I suggest, value the longer-term network possibilities (keeping our history, happenstance links to distant relatives, curating lots of photos, etc). This makes us more vulnerable to the manipulations of the companies, who can begin to mess with our message feed and we feel stuck, unable to give up on the sunk costs of our personal investment in a particular platform. Younger folk would just switch, and escape!
I noted also this week that younger people are more likely to use ad-blocker software (http://www.djsresearch.co.uk/InformationTechnologyMarketResearchInsightsAndFindings/article/Millennials-most-likely-to-use-ad-blocking-software-survey-finds-02377) suggesting a greater willingness to use 'resistant' software to counter the big platforms. Perhaps there's some hope there that the imbalance of power could tip a little more in favour of the public.
As you suggest, we may not be locked into an ever growing world of corporate power, simply, since this power itself breeds the means (social, literate, technical) by which people can resist. That means, I think, that as education increasingly occurs on proprietary platforms, teachers must increasingly take a stance in managing and resisting the ab/uses of platform power....