There were places to organize before Twitter. There will be places after. They could use Mastodon Lemmy or any other activity pub client. They could use a BBS or a php powered forum or an email mailing list. The only thing special about Twitter was that so many people were accessible via it. But musk doesn’t want them there anymore. He’s doing everything he can to tell everyone that. So there’s no reason to stay for the sake of the platform.