I'd argue Twitter is just as complex, because Twitter's product is its users and the content they create, where the others are governed by the laws of physics and making a good car (i have one, they're good!). What you have is a bunch of engineers on twitter going "ah yes, its just a social network feed! I wrote that in CS244 as my class project. how hard could it be", forgetting that twitter is an international network with tens of thousands of hyper targeted communities that feed off each other, diplomats that negotiate with governments and communities, etc. Not to say that this is impossible for anyone else to make, but it's a lot harder than just launching a site with your hundred engineers. i'd recommend reading platformer.news for a good