A slide has two possible jobs and they pull in opposite directions.
A presented deck supports a speaker. The audience is listening, so the slide carries the minimum that a listener needs to follow: an action title, one exhibit, a handful of labels. Thirty words is generous. Everything else is in the speaker's mouth and in the notes.
A reading deck is a document with a deck's page shape. Nobody is speaking, so the slide carries the whole argument in text. Three hundred words is normal, and the reader controls the pace. It circulates in advance and survives forwarding. Each reader reads it alone.
Why can't one deck do both jobs?
The hybrid tries to serve both and fails at a rate you can compute. Put 180 words on a slide and stand in front of it. Your audience reads those words silently at 220 words a minute, finishing in 49 seconds. You say them aloud at 130 words a minute, finishing in 83 seconds. For 34 seconds of every 83, which is 41% of the time you're speaking, your audience has finished the slide and is waiting for you, reading ahead, or checking mail. Across fourteen such slides, the deck takes 19.4 minutes to say and 11.5 minutes to read, and the audience spends the difference somewhere other than with you. If you've ever sat through one of those meetings, you'll know what the room was doing instead.
That arithmetic is the case against the dense presented slide, and it's worth carrying because it converts a matter of taste into a matter of seconds. The room is bored because it finished reading before you finished talking, every single slide, for forty minutes. Ugly slides have little to do with it.
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Why does a serious deck often need two versions?
The practical consequence is that a serious deck is often two artefacts. The board pack that circulates 48 hours ahead is nine pages of 340 words, 3,060 words in total, read in about 14 minutes by anyone who chooses to. The version shown in the room is fourteen slides at about 31 words each, 434 words on screen against roughly 3,900 spoken in a thirty-minute slot, which puts about 11% of what's said in front of the eye and the rest in the ear. Building both costs more than building one. Building one that does both costs your audience's attention, which is a bill you never see itemised.
There's a third artefact people forget: the deck after the meeting, forwarded to someone who wasn't there. A presented deck fails that reader completely, because the speaker is missing and the slides were built assuming a speaker. Either send the reading version, or write speaker notes dense enough that the slide plus its notes reconstruct the argument. Deciding which, in advance, is part of choosing the medium.