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.
I think you are still failing to understand section 230. 230 does not regulate the relationship between two businesses. It is 100% irrelevant to the relationship between AWS and Parler. It had no effect, and if it's repealed, it would have no future effect on AWS kicking other businesses of their site.
Section 230 limits who can sue Parler for content published on their site. Without 230 Parler (and Free Republic) would be worse off, because they could get sued for anything the users post. The First Amendment isn't a liability shield. The simple question is whether sites like Free Republic and Parler should be liable for 100% of the things said on the platform. If they are, they will be driven out of business. Is Jim Robinson the editor of Free Republic and legally responsible for what you say? That's what repealing section 230 would do.