Correct. I shared this thought because I believed that the realisation that most websites are simply database frontends was an unique, interesting and somewhat liberating thought.

I apologize if it feels like I'm stating the obvious, but it was a startling realisation to me.

I always kept each site/company in their separate boxes, when in fact they all do rather similar things, with different branding.

Yes, since the 1970s or perhaps earlier, most computer software has been "forms" (screens for a user to enter some information to be stored in a DB) and "reports" (screens that present information stored in a DB to the user). That's it. Green screens, client-server, web sites, etc are all variations on a theme.

The "social network" aspects of FB could perfectly well have been done on an IBM mainframe with 3270 terminals running IMS, 40 years ago.