What you are saying is that UML is not really visual but rather a kind of text. This got me thinking. The text I am writing here is also on one level just text - but I see it as a visual representation of black dots on a white background. But I think the point of diagrams is to be really visual and of text to be text.
Only if you store them inefficiently.
> Just compare a gif of a diagram and its description.
A bitmap image (GIF or otherwise) is an inefficient way to store a diagram. For a purely semantic diagram, the source it represents minus anything not actually represented in the diagram is sufficient; if you have additional presentational information you need that, too. For a diagram-specific format, something like graphviz or mermaid source is a possible representation.