Easy interop with legacy code is how kotlin took off, so maybe it will work out?
Good interop was a requirement for widespread adoption, but not the reason why programmers want to use it. There’s also null safety, a much nicer syntax, custom DSLs, sealed classes, type inference, data classes, named and optional arguments, template strings, multi-line strings, computed properties, arbitrary-arity function types, delegation, custom operators, operator overloading, structural equality, destructuring, extension methods, inline functions and non-local control flow, reified types, …
Some of these features have since been added to Java.
It is well supported in all browsers and operating systems. At least VS Code and IntelliJ support it, and even some terminals.