Current real life scientist in biomedicine:

"Interesting but I don't know how to make sense of it. How can it be that "close to nothing of what makes science actually work is published as text on the web"?"

I'm not convinced this assertion is true. Difficult to parse by a non-expert? Sure. Often stored in pictures rather than text? Absolutely - indeed, a number of journals directly ask reviewers if the text and graphs are duplicative and consider this a negative. Harder to "disrupt" and monetize than many companies have expected it to be? Certainly.

"Is the information that makes science actually work mostly in images that the machines don't yet understand?"

In my mind, this is the most credible bit of the author's complaints. A lot of science in biomedicine is done in information dense graphics. The author picks especially hard to approach ones, but this is definitely a thing.

"Was the information paywalled or in private databases and inaccessible to this researcher?"

For an outsider without institutional access to journals, this can be a problem. More acutely, there is some lag between "What I'm currently working on" and "What's in the literature" simply because the literature is slow (and has gotten way slower during the pandemic).

"Are the papers mostly just advertisements for researchers to come gab with each other at conferences and doodle on cocktail napkins, and that's where all the "real science" happens?"

In biomedicine, papers are the product. Conferences tend to have a couple uses:

1) Previews of coming attractions - things I'm working on that are close enough to done to talk about, but not so close as to be making the rounds yet. These talks will often have less detail than a paper would, because we've all sat through a presentation that does into a ton of implementation detail and they're agonizing. Also I only have fifteen minutes.

2) Looking for postdocs - either from the hiring or seeking end.

3) Building professional networks - this is mostly so when someone comes to me with a problem, I know who might be working on say...causal inference with time-varying exposures...and can reach out to them. Usually to ask what papers I should read to get caught up. Or to bring them in on a paper/grand proposal.

4) Looking for problems other people are having that I can solve, and then reaching out.

"(From the comments) is the information needed to make sense of papers communicated privately or orally from PI's to postdocs and grad students, or within industrial research labs?"

Only insofar as my graduate students and postdocs have access to my time and expertise, and a job that is expressly meant to encourage understanding things. "I don't know, why don't you spend a couple weeks figuring out how they did that" is a perfectly good use of a graduate student's time, but something I find is rarely encouraged elsewhere.

"Don't real scientists mostly learn how to think about their fields by reading textbooks and papers? (This is a genuine question.) If so, isn't it likely that our tools just aren't advanced enough to learn like humans do? If not, what do humans use to learn how to think about science that's missing from textbooks and papers?"

One of the things that's likely missing, because those are all finished products, is the process. For example, I spent an hour chatting with a graduate student about three or four different ways they can approach their problem - what assumptions come with each one, tradeoffs, etc. But only the branch that actually got used is going to be published.