The ability of a non-scientist to understand a paper at a useful level varies greatly based on the area of study and the reader's knowledge of the topic. 'Basic scientific literacy' may not be enough, but there are many more individuals with an amateur level of advanced understanding or interest in a given area who benefit greatly. I personally have no institutional access but I read a lot of papers that I can understand with an undergrad level of science background and a keen interest in a specific subject. I'm sure there are many others like this.

And let us not forget those who ended up working in wildly different fields from their degree or degrees. Such "cross-pollination" between different fields can be very productive.

"Basic scientific Literacy" here probably should include basic understanding of statistics, and knowledge on how to read a journal paper in a foreign scientific domain. You don't have to know the lay of the land in a particular domain to understand the specific claim or methodology outlined, knowing how much it may mean in a domain. . . well that is context determined.

> (in part because most papers are badly written and need familiarity with the genre to be understood)

Considering science is a community/social enterprise, it's surprising that such papers are published at all.