ChatGPT is good at writing fluent text because there is lots of quality text around on the Internet to train it on. Most text online is at least grammatically correct, and a subset of online content is of some decent quality at a story level (books, reports, professional news websites, etc.) . Midjourney can make up great images because there are lots of images around to train it on, they do not even have to be that good in terms of composition, the pixels in an image add up to an accurate representation of something.
Now with presentations though…. There are fewer of them around online, and most of these are actually not that good. Even if you were to feed let’s say McKinsey’s entire archive of decks into an AI model, would it be able to produce a McKinsey-style deck based on a prompt? Maybe. But the result would be a consulting-style, dense document, not an engaging pitch deck.