Section 230 says that "No provider or user of an interactive computer service shall be treated as the publisher or speaker of any information provided by another information content provider" (47 U.S.C. ยง 230). In other words, online intermediaries that host or republish speech are protected against a range of laws that might otherwise be used to hold them legally responsible for what others say and do. The protected intermediaries include not only regular Internet Service Providers (ISPs), but also a range of "interactive computer service providers," including basically any online service that publishes third-party content.
Without Section 230, Free Republic becomes the de facto publisher of the user content, and is responsible for it. So if you accuse Person X of being a pedophile, they could sue you AND Free Republic. With section 230, FR isn't liable for what users say.
AWS did not have an at-will agreement with Parler, and they lied about Parler violating any terms of service with respect to content, thus treating them as publisher in spite of whatever Section 230 may say.
The matter of publisher versus platform when it comes to YouTube does not protect that platform’s content providers either. Hence an ongoing migration to Rumble et al.
Not very convincing that Section 230 protects any platform and/or that its wording will undermine all online platforms; there are multifarious other laws in effect that can provide protections, particularly the First Amendment.