I likewise feel that the Economist article has articulated what I was trying to say.
I agree with your point on the platforms not striving to inform, their business models is to drive volume only. However, whether they like it or not, the disruption they have created has put them in a position where they have disproportionate power to allow or prevent differing points of view to reach people. This is why I believe the huge players like Google, FB, Microsoft and Twitter should be viewed differently than the rest of the web.
On the consumer side, Google, FB and Twitter should be considered to have oligopoly status and on the business side I would add Microsoft into that mix.
As a side note, the total domination of ‘sustaining user attention’ as the driver, has allowed the platforms to be both manipulated by outside forces (2016 election tampering), reinforced the tensions tearing at all countries and magnified the bubbles that everyone operates in. Curiously, they also had/have it in their technical power to ensure that divergent points of view could be presented to users. Each of these organizations has chosen not to do this.