>they let people read their articles for free? This is puzzling to me.

That's the data use consent part...which the article talked about:

>We see a handful of large platforms harvesting users’ private data to share with commercial brokers

>On many platforms, we are no longer the customers, but instead have become the product. Our data, even if anonymised, is sold on to actors we never intended it to reach, who can then target us with content and advertising.

...hence irony. Guardian is either pay or agree to data use