I can't agree with that.
eCharts is good, but https://plotly.com/javascript/ is also super nice and I am actively following https://observablehq.com/plot/ which seems on a path to true greatness.
I particularly "like" the way they have multiple APIs and inconsistent examples across them. Would it kill you to have the same examples in each?
That being said, i generally like the library but the docs are bad.