Safari has one of the best Web Components implementations, with excellent Shadow DOM and Custom Elements compliant to the latest spec in the Safari 10.1 beta. T

Safari has one of the best Web Components implementations, with excellent Shadow DOM and Custom Elements compliant to the latest spec in the Safari 10.1 beta. These are the two most essential Web Components specs. By comparison, Edge doesn't have either, and Firefox has no Shadow DOM and old out-of-spec Custom Elements. How is it that Safari is holding the web back in this area? (WebUSB and WebMIDI have nothing to do with Web Components, they are hardware-specific device APIs.)