Self-expression is the internalization of social authority, not the externalization of a “true identity”
The more that individuals express through these codified, networked, formatted means to construct a "personal brand" identity, the more they self-assimilate, adopting the incentive structures of capitalist social order as their own. (The machinations of Big Data make this more obvious. The more data you supply, the more the algorithms can determine your reality.)
how production in social media is often sold to users of these platforms as self-expressive creativity, as self-discovery, as an elaboration of the self even, but it is really a narrowing of the self to the reductive, defensive aim of getting recognition, reassurance of one's own existence, that one belongs.
Validation is nice, but as a goal for creative effort, it is somewhat limited. The quest for validation must inevitably restrict itself to the tools of attracting attention: the blunt instruments of novelty and prurience ("Kanye West in a balloon chair"). The self one tries to express tends to be new, exciting, confessional, sexy, etc., because it plays as an advertisement. Identity is a series of ads for a product that doesn't exist.
It's hard to escape the idea of a "connected world" all around you, and there is no denying that being online metes out "connectedness" in measured, addictive doses. But those doses contain real sociality, and they are reshaping society collectively. Whether or not you use social media personally, your social being is affected by that reshaping. You don't get to leave all of society's preoccupations behind.