Section 230 was explicitly about allowing service providers to act in an editorial capacity, allowing them to remove content that they deemed offensive. The alternative was what happened in two court cases: moderate things and be liable for anything that slips through or moderate nothing and don't be liable for anything but the service fills with spam and other unwanted content and becomes unusable/not family friendly.

It was never about a platform being treated as a mere carrier, it was the exact opposite: allowing them to moderate without huge liability fears.