Some of these new HTML features don't fully work in my "ancient" browser. But all of them partially work (ie opening the accordion element doesn't close others

Some of these new HTML features don't fully work in my "ancient" browser. But all of them partially work (ie opening the accordion element doesn't close others but it still opens and closes) and they still remain functional elements I can read and interact with. This puts them far ahead of any javascript implementation which almost universally fail to nothing.