And, why should a new developer on fresh projects use it? It seems ES6 and latest CSS specs should cover everything JQuery used to be used for.

Plus, wouldn't actually using Vanilla JS be faster?

Right now it looks like people use JQuery for legacy code. But, they give no reason to use it for new projects, except if they need it for other libraries they're going to use. (based on legacy code anyways...)

JQuery looks redundant in the modern Javascript era on evergreen browsers.