Beautiful charts, shame it looks defunct now.
Did you even look at echarts demos, or amcharts demos for that matter -- it's basically the same thing, but paid for: https://www.amcharts.com/demos ?
I don't have anything against charts.css, but it's like comparing a children's plastic toy to a real space shuttle. I spend most of my work hours developing a heavy business analytics application (not unlike Apache Superset), and it would simply be impossible to implement it with something like chart.css
I'm using ECharts (and happy with it) but there are some places where I want like a sparkline in every row of a data table, which is a lot of ECharts instances to instantiate, and this lib looks like it'd be great for that.
If there are a huge number of datapoints, this library will paint itself in the corner.