I know it's a bit hand-wavy to conflate their use of Discord and reddit for formal organizing with the failures of the organizational model, but at its root the choice to use these convenient, corporate platforms is vested in the problem of its rise and fall: it is and was a movement of convenience, not principle. Using Discord for something that important is unprincipled.
It is, of course, one thing to educate people on how to migrate to and use technologies and platforms that _aren't_ selling us out; moving large communities over from Discord to e.g. IRC is incredibly nontrivial from a social standpoint.
The other part is we need to make people aware of how dangerous this data goldmining is for survival under capital. The only real example I can give is how insurance providers can, and probably do, use purchase data to hike premiums on at-risk people.
Or, howabout, imagine if police departments began creating profiles of people based on their interests exposed through internet data collection, and started pre-emptively monitoring and surveilling people who are "prone to crime". You can immediately imagine how this might be used to enforce hierarchies and systemic abuses.
Moving away from the platforms that have sucked us in and exploited us, at a scale big enough to send a clear, revolutionary message to capital, is going to take principles, not convenience; it's going to take us collectively deciding that no matter the convenience of corporate walled garden platforms, we need to stick to communications mediums that reflect the freedom we want that we do not have under capital.
Many options exist, but they are withering away, and inertia is hell to fight.