Again, the Internet itself is the street.

Internet is a bunch of compters connected together. Social media sites are a part of the internet. If you say internet itself is a street, then social media sites are part of that street as well. If you're just thinking about just the supporting infrastructure like cables, routers and switches, a lot of them belong to private companies as well. So you're talking about a street in a gated community, then you shouldn't expect any attributes of public space there either. Do you see that diiferentiating social media sites from public spaces just because they are owned by companies fail very quickly when you apply the reasoning consistently? Internet is quickly approaching the status of a basic human right, yet most of it is owned by private companies.

Do you know what's equivalent to malls and Walmart on internet? That's Amazon, eBay and Alibaba.

What's the analogy to a real world place people go to express themselves, protest and engage with the broader society? The closest I can think of is a town square.

So a better analogy in my opinion is,

1. Cables, satellites, routers and switches: Streets
2. Online news websites (Vox.com The Verge etc): Newspapers
3. Streaming video and audio sites: TV and radio
4. Malls, and supermarkets: Online shopping sites
5. Social media: Town square