Many excellent presenters use a slide as a 2D canvas on which text and images can be placed in arbitrary locations - whatever best helps get the ideas across to the audience. Is losing this feature worth the advantages of this tool?
To answer your question directly, I am already all-in on Markdown and lightweight markup languages in general. Adopting such a thing is an exercise in a certain form of minimalism. In Markdown I can theoretically do anything by dropping into HTML, but the entire point (to me) is to focus on what I'm trying to write and not on every presentation and every slide being unique objects.
It's the same thing with my blog. I could use any number of tools that give me arbitrary control over text and images appearing wherever I want. But I choose not to want that in exchange for the simplicity and constraints guiding me to focus on what I'm trying to say rather than how I'm trying to say it.
I have found a local maximum for me, and tools like this are a good fit for that. You may be elsewhere enjoying a different kind of local maximum.
The same tradeoffs apply to a text-based diagram tool like mermaid.js vs more traditional diagramming tools like Miro.
My coworkers' Miro diagrams are prettier than my mermaid diagrams. But mine are composable and able to be versional controlled. I'm able to create complex diagrams many times faster using a text-based tool.
Ultimately, slides and diagrams are for conveying knowledge. If you're able to convey the same knowledge with significantly less effort, that outweighs the loss of "style points" in most situations (internal knowledge-transfer, meet-ups, etc).
I like md, and I like mermaid, and I like text / simple. But I know to help others, sometimes the visual medium and storytelling justify the alternatives.