I don't think parent meant to say that the technology behind Facebook is trivial. Just that it's trivial when contrasted with a bunch of technologies that are at best in prototype stage.

A decade-long life extension or growing meat without animals would both probably involve more "Hard Tech" style innovation than building Facebook.

Other observations are IMO less pat. E.g. designing cheaper/better sensors could be either harder or significantly easier than building a Facebook. Depending on the type of sensor and the cost improvement.

A lot of the FB tech circa 2010 seemed to be reinvented versions of things ex-Google FB staff used. They've done a lot of innovation since then though.

Which is absolutely true if there were no such thing as the NBA. Being good at Donkey Kong is also difficult.