Every so often when I am googling for something related to Mastodon I run across this Mashable article about how MASTODON IS INHERENTLY DOOMED and I just giggle.
Here's a few I've been using with some degree of success:
"it's like twitter with less nazis"
"it's like twitter except it's run by whoever wants to help run it instead of by a bunch of silicon valley techbros whose paychecks come from adviews"
and if she was online in the early 90s, "it's the bastard child of Twitter and FidoNET"