Malls aren't and have never been the primary space used for public social discourse and commentary. Today, such discourse increasingly happens online, and it's increasingly true that sites like Facebook and Twitter actually are the primary space for public discourse.
It's really never before happened in history where a private company has become the mediator and facilitator of discourse involving millions of people simultaneously. Previous forms of media had extremely restricted participation roles in comparison. Newspapers, TV, and radio can all only publish a relatively tiny amount of content, so the idea that millions of people could simultaneously publish content to those platforms was never viable; they were only capable of pushing out content from a few folks to many, but they were never many-to-many. This almost infinitely scalable many-to-many communication property of modern social media makes it feel much more like a public space than newspapers, TV, and radio ever did.