A serious presentation takes three different crafts: the argument, the design, and the build. They’re not three versions of the same skill, and almost nobody is excellent at all three.
Most presentation designers are hired for the middle one and discover the other two on the job. That’s how you end up with one of two decks. A beautiful one that argues nothing, or a smart one that looks like it was made in 2011. Neither gets you the yes.
The third craft is the one nobody warns you about. A 60-slide deck is a piece of software as much as a piece of design. It has master slides, inherited templates, linked charts, and six people with editing access. Get the build wrong and it falls apart on the morning it matters.