It's useful for local events, but very expensive for organisers ($15 a month for a basic events page). People pay purely because others use it, an open alternative would be 👍
Meetup's "network effect" might be overcome because it isn't a global network (e.g. someone in London is only going to care about meetups in London).
Also, an open alternative would be perfect fit for #federation, each community having its own instance.
social.coop is a cooperatively-run corner of the Fediverse. The instance is democratically governed by its members, who generally share an interest in the co-op model, but topics of discussion range widely.
Our instance is supported by sliding scale contributions of $1-10/mo made via Open Collective. You must have an active Open Collective account to apply for membership; you may set one up here