From my perspective are the looks the biggest drawback of Graphviz. Having a few standard templates to choose from for a graph would be great. As an example, if you could with one parameter turn the visuals into a Mermaid diagram.
I don’t see the wasm size as a real problem. It is compressed 388KB, uncompressed about double. (Details · Discussion #87 · hpcc-systems/hpcc-js-wasm · GitHub)
(but only my 5p).