Compuserve and a number of other credible alternatives to AOL existed during that time. Usenet and BBSes also existed. Myspace and Facebook (initially) were only for teenagers, college students, and people who never grew out of those phases. You might as well put Livejournal in this list, because none of those platforms (at those times) were as effective at corralling and suppressing wrongthink as Twitter and Facebook have been today.
Apart from their obligations under the law, AOL did not police content. In one example, AOL banned explicit discussions of homosexual activity but did not ban anti-homosexual hate speech. They policed the first type of speech because the CDA required them to prevent the transmission of explicit material to minors, but they did not police the second type of speech because it was not illegal.
Facebook and Twitter are actively policing speech that is not illegal.
