i guess another core thing is people taking "social networks" as a noun seriously.
they're social network managers, your social network is just the graph of everyone you know and what they're writing to the web.
but you have to build those things off-site, or at least know where to find each other elsewhere, or you will always be at the whims of whatever site, and attached to the sites in ways I'd say are probably unhealthy.
Twitter isn't what made Twitter work, Twitter worked in spite of Twitter. same with Tumblr. mastodon arguably works, but only because most people worked around the creator.
the platforms are coffee shops, bars, in the case of mastodon they're closer to community centers. whether they're chain or locally owned doesn't change the fact that you aren't actually going to them to just buy coffee.
platforms are the substrate and atmosphere, but they aren't the people, and forgetting that part leads to a lot of unnecessary strife.
it's extra work, sure, but so is everything that doesn't have bigcorp money in it. or even smallbiz/coöp.
I've seen people get hurt a lot when they have to move, having this in mind when you're making connections helps. it sucks that it's more effort, but that's adulthood i guess.
a rolodex can always be used, a spurious ban or a platform closing can disconnect you from everything you've built. i have maybe 10% of the people I knows contact info, but i have the handles of the rest stored elsewhere and can almost certainly find them by that pseudonym, or at least by asking around, if I had to. I've had people I haven't talked to in five years pick up as if we never left off, many many times. I wish we talked more, outside of crises, but we have very different lives and have drifted. but we're still around and talk to each other when the shit hits the fan.
the power of the Internet is the connections, not where they're happening. don't let someone else control the key ones.