> Slides have two distinct purposes: as a part of a presentation...

Many years ago I went to a presentation on giving good presentations, focusing on making good slide decks. (It's currently annoying me that I can't remember where this was, even though I can picture the room in my head.)

The presenter had a short example slide deck, and gave a mock technical presentation using it.

The deck had a different, eye-catching background image for each slide, chosen to be noticeable, but not dominate attention, and be well-suited color-wise for any text or images to be placed on top of the background. The presenter suggested that the background image didn't need to have anything to do with the content of the slide, and that it's mainly there for its general visual impact. The slides were not uniformly designed. It wasn't like someone had used a template where the title, text, images, etc. were all in the same or similar places on each slide. The most noticeable part of this was putting the title in different places. This variety was in itself engaging.

The slides themselves were very light on text, and were mostly about presenting charts, graphs, tabular data, or images relevant to the talk. When there was text, the presenter never read the text verbatim (or sometimes even at all); the text there was a jumping-off point to discuss in detail whatever the topic of the slide was. The argument there was that people know how to read, can read in their heads faster than you can read to them out loud, and if you're just going to read slides to them, you don't need to present it and you should instead just email a document for your attendees to read, and skip the presentation entirely.

Finally, the slide deck itself did not have all that many slides. The presenter dwelled on each slide a lot longer than I've seen in most presentations. The slides were more guideposts to mark the overall topics and outline of the presentation, to provide milestones and transitions. For the most part, the presentation could have been done without the slides at all; the slides were there to add visual flair, help keep attention, and (occasionally) prevent data or images that would be easier to understand visually rather than spoken.

Ultimately I found the mock presentation given to be incredibly engaging, much more so than the vast majority of presentations I'd attended before or have attended since, and I remember that the topic wasn't even something that would usually hold my interest so tightly. I very rarely gave/give presentations, but I've tried to take all this to heart when I had the opportunity to do so. I don't think I ever really did the variety-of-background-images thing (honestly, I never enjoyed giving presentations, and treated it as a chore, and never felt motivated enough to find a bunch of suitable background images). But I at least always tried to keep text to a minimum, so the meat of my talk would be in what I was saying out loud. I wouldn't call myself a particularly good presenter or public speaker, but I think my talks were better than they otherwise would have been.

> Slides have two distinct purposes: [...] as a way to learn or review material outside of the presentation

I've come to think that slides aren't very good for this second purpose, and probably shouldn't be. The information density is never going to be high enough, and if it is, that's going to make for a terrible slide during the presentation. I would much rather read a transcript of the talk later, or, better, a detailed summary. If the slides have charts or other data, then sure, it's useful to have those outside of the talk, but those can also be inserted in-line into the transcript or summary.

I get that it's more work to write up a transcript or summary (and I know I myself would probably balk at having to do this), but if you've prepared properly for the presentation, you probably already more or less have something approaching a transcript in your talk notes. Cleaning them up for publication isn't zero effort, of course, but it should be much less work than writing something from scratch.