Visuals help people retain info. At the very least, slides that contain 1-2 sentences that state your main idea for that section would help. Having lots of text is a great way to get people to ignore what you’re saying and read the slides so don’t do that. But best of all is simple, clear graphics that help communicate your main points.

I recently attended a talk [1] by Robert C. Martin where he spoke eloquently and astutely for over an hour on the subjects contained in the diagram on a single slide. Afterwards, I was impressed by the quality and content of the talk, and didn't feel like I'd been hypnotised by yet another slide-by-slide "presentation".

A well-given talk should not require its contents to be summarized as it is being given. Pictures are worth a thousand words, so technical diagrams are an obvious exception (there are others) to that.

[1] https://skillsmatter.com/meetups/11368-an-evening-with-uncle...

No, but they definitely help. My rule on this is that slides should make it easier to follow a talk and get back on track if your attention wanders. If the slides require extensive explanation then the information is probably better summarized in the talk and laid out in greater detail in a paper.

Obviously a lot depends on your audience. Slides at an academic symposium can be dense enough that you can get the gist of the talk from just looking at the slide deck, slides for an introductory talk on a subject should be more like the list of contents in a book.

The question is too broad to answer with yes or no.

If you can come up with slides that make it easier for your audience to follow you, go for it.