The idea that the planet is wounded due to too many people and needs to be "healed" is complete nonsense. We aren't close to carrying capacity. You're taking various complaints ("immigration policy," "no support for women," "people work too much") and connecting them to a totally unrelated phenomenon (declining population). People are not deciding against children for rational reasons.

I think it mostly has to do with social atomization. Cultures have always supported marriage and childcare. That's less true around the world. As a result people are getting married less often and having fewer children, often against their own desires.