Actually, "desugaring" is a thing. It's a backport of those new parts of the standard library that the dex converter inserts into your app. Currently, it's only Java 8, but I had no trouble building an app that uses Java 17. You just can't use any features that rely on new classes or methods, like records. But purely syntactical ones do work flawlessly.

I don't like Kotlin because of how much it tries to do in the language itself with maximally terse syntax, and because of its asinine defaults like final-by-default classes and immutable-by-default everything. Java's sugar is much better thought out.