Done right, they're faster, for sure. But when you use Electron you're leveraging thousands of man-years of Google developer effort to build a web browser that works consistently and well across different platforms. Although the web platform gets a bad rep for cross-browser compatibility problems and general weirdness, a huge amount of that goes away when you target a single runtime. Suddenly you can use every half-baked Chromium API and prefixed CSS feature without worrying about how it's going to break in IE 11.
In that situation, you suddenly realise just how much power the web platform give you. You can style any element, any way you want. You have you have a complete, out-of-the-box object model for your whole UI, plus developer tools to help you debug it. You have advanced typography control. You can drop a canvas element in and get an immediate-mode 2D or 3D graphics API. You can layout stuff in flexbox or grid, or just as a plain old document (which most toolkits would delegate to an embedded web browser anyway).
There are better languages that JS, that's true. But whether there are truly better cross-platform app toolkits than the web is, in my opinion, rather more unclear.
