With Section 230 protection, the platforms don't have to remove defamatory material -- they can just tell people to get lost even if the material is unambiguously false and damaging
You have something posted on your site by a 3rd party. Someone sends you a takedown request that explains exactly what is defamatory and why. How can it be so hard to either take the material down or make a judgement that it can be safely ignored?
Your call, print and broadcast outlets make this determination ALL THE TIME. I wouldn't think that people running Internet platforms are so much less competent.