They already walking back their massive own-goal:

https://www.meetup.com/lp/paymentchanges

UPDATE October 15, 2019 1:30 pm ET

This payment change is currently only a limited test for a small number of groups. Organizers of these select groups have the option to opt-out of this test. We will not be making any significant payment changes in the near term. We are committed to providing advance notice before any changes go into effect.

We’ve also updated our FAQs below to address specific questions.