My main complaint is the treatment of generics and lack of value types, which are actually two sides of the same coin.

Another thing I'd like to see is opt-in null safety. The Optional type is a very good mechanism, but when every reference is potentially null, its ability to enhance language safety is limited.

Other than that, it has everything I want. And of course, the ecosystem, tooling, etc. is simply the best in class.

My personal preference is for ML-style languages, so Java will never be my true love. But as far as languages go, you can do much worse.