tl;dr When browsers start to adapt proposals from Open UI, it might not be necessary to use any 3rd party libraries to have nice components and controls in web applications e.g. selects. It would require only a minimum of CSS and Javascript to get them working and looking good.
The purpose of the Open UI, a W3C Community Group, is to allow web developers to style and extend built-in web UI components and controls, such as dropdowns, checkboxes, radio buttons, and date/color pickers.
To do that, we’ll need to fully specify the component parts, states, and behaviors of the built-in controls, as well as necessary accessibility requirements, and provide test suites to ensure compatibility. We’ll also implement polyfills for our extensible web UI controls.
Today, component frameworks and design systems reinvent common web UI controls to give designers full control over their appearance and behavior. We hope to make it unnecessary to reinvent built-in UI controls, but for those who choose to do so, we expect that these design systems will benefit from Open UI’s specifications and test suites.
Long term, we hope that Open UI will establish a standard process for developing high-quality UI controls suitable for addition to the web platform.