The browser renders it's own GUI too, it's not OS native
The browser uses lots of resources too.
The browser is kind of a plugin to the OS and must be updated separately.
Java nowadays is pretty fast too.
Java VM serves a platform for multiple languages like Scala, Kotlin, Clojure.
Let's face it, the browser is the new JVM and a soon it gets the same permissions like the JVM to access the file system and such, we get the same problems.