As far as I’m concerned, for a capitalist, the "optimization" in "optimization for engagement" means "make X do Y as intensively as possible, regardless of their human rights". User metrics don’t necessarily imply it, silly me.
To emphasize a bit, the "optimization" in "optimization for engagement" means that it isn’t meant to be manageable by marginalized people, which is very different from post-capitalistic services like Bonfire (or XMPP, IRC, or tabletop games, bookshops… places and activities famously biased towards conviviality).
This is a bonfire demo instance for testing purposes
Manual federation enabled