You can't easily improve a language and stay compatible with the previous versions. C++ does it but they are crazy.

you would think there would be some kind of universal language

It does not exist, but anyone is free to try and invent it. It should be low-level like assembly and high-level like BASIC, functional, object-oriented, and have weird stuff like traits, concepts, and alien features from Haskell. It must also have both the pointers/references of C++, and the borrow checker of Rust. And don't forget to make it as secure as Ada with pre and post conditions. But it must still be easy to use. Also you will have to write a compiler for every operating system ever (mainframe, server, desktop, iOS, Android, every phone, every tablet), and contain a universal GUI that pleases everyone. It's literally impossible to do right now.

Last but not least, Java was supposed to be this universal language that you can run everywhere. It failed and it cannot be run everywhere. It also had to be improved a lot, and it's missing a fuckton of features from every other language.