This is something that I've been intrigued about too. Most of the cli/text based creation tools out there focus on text based content as well. But, for many people myself included, the desire is really for a text based creation tool that focuses on image or diagram based output. Features like auto tiling (with priority) of images on a slide would be useful.

So many people end up writing what should be their presentation notes as their slide content. Personally I think you're better off with a holding image and move your content to the presenter notes section.

I've used revealjs.com and hovercraft [1] in the past but usually end up on GSuite Slides to throw things together quickly. Slides (like PowerPoint) can't do branching presentation paths though :(

[1] https://github.com/regebro/hovercraft