This is true, but it does take certain qualities in the slides, such as not re-stating what is being said word for word, and including relevant & enlightening graphics that show what the speaker cannot say.
Of course, you could argue knowing how to make such a slideshow is part of being a good speaker, because it is all about creating a slideshow to support, augment, improve & fill the holes in your talk.
I fortunately have not been in a position to attend a large number of presentations. Of the ones I have attended, the best have been by well-prepared speakers who use a whiteboard and no slides. The diagrams tend to be crude but hand-drawing on a whiteboard hardly ever outraces the ability of the audience to follow along; with slides the opposite is often the case (for me anyway).
Of course, you could argue knowing how to make such a slideshow is part of being a good speaker, because it is all about creating a slideshow to support, augment, improve & fill the holes in your talk.