Large centralized platforms are far far less likely to shut down than small, compartmentalized instances....
edit: Take Lemmy for instance, there's tons of new instances starting up, but many will likely end up shutting down, because the reality is, hosting a service is serious work. Most people don't actually know what's involved in hosting something like this.
The solution for that is simple. Either self-host your own instance OR choose an instance where you can support (with money) the team hosting the instance.