i feel like it's actually just an incestuous mix of thinking you are better than tiktok but still holding onto an immature version of yourself by being on instagram.
maybe i just see social media use as an inherently immature thing? (including lemmy)
i guess its a media that is intended for social use, but i feel thays similar to calling a cooked meal "processed food". like yeah technically correct (best kind), but also defying the indended meaning when most people use the term.
I'm not them but for me "social media" in the colloquial use has some sort of discoverability and some functionality to put out a piece of media publically in a way that can then be discovered. (Note that this isn't my entire definition, just the part where I feel email is disqualified.)
For emails you need external services to find, subscribe and/or manage things such as mailinglists to sorta approach this behavior.
I think social media can be used for a large variety of things. Many important movements (50501 for a current example) greatly rely on social media to mobilize folks.