Here's a thought: I am purely hypothetically able to sell some previously unknown and unforeseen (therefore legal) opioid agonist that is just as addictive and dangerous as heroin with no issues of legality. Or maybe it isn't even an opioid agonist and has some novel mechanism of action that is yet unknown.
What's the solution? New legislation that adapts to such a threat to societal welfare. And this is what is effectively happening here with litigation over Section 230 et al. (worth mentioning that it's not even the case that Twitter's business model involves working around the law; Section 230 _is_ the law and it shields Twitter from liability. So there is really no case here like you are describing to begin with.)
The end of society and government is more or less to identify and avoid bad societal outcomes, and an evolving legal system is necessary to keep up with technological and social changes in the world. Maybe you are correct and Twitter shouldn't exist to begin with, alas Twitter exists and other things like Twitter exist. They aren't currently in grave violation of any law to my knowledge, and any law that is to be enacted regarding things like Twitter should be written in light of the current state of the world, which is that Twitter exists and that things like Twitter are easy to create.