Hard not to reflexively reference the XKCD here. I think the authors of most charting languages would say they look good by default. It seems more likely this is achieving a subjectively different presentation than something objectively better. Higher level implies information loss. So it can only be better if it is doing so by assuming some better defaults. But then you have to ask if it lost expressiveness.
We find an additional dimension where previous language doesn't explicitly use (semantic type) as the key part of the specification, which turned out to be the root reason of why certain low-level parameters are set.
Effectively Flint is designed to specify charts using another set of semantic parameters over geometric parameters, which happens to be something AI are pretty good at! (They can based on field names + sample values to infer the semantic types reliably than guessing geometrical params.
Btw, for others reading this comment, this is the XKCD we are talking about! https://xkcd.com/927/