&gt;  I do not think most Java programmers regularly care about the lack of abstractions like higher-kinded or union types. Would be nice to have, but never have I felt like I needed them.<p>That could be stated about pretty much every feature added since Java 1 really, it&#x27;s not like the blub paradox has disappeared from our reality. How do you know that you wanted union types when you&#x27;ve never used a language which had them (and had features hindering such a conceptualisation, C-style enums are not really helpful there, even less so when extended the way Java did)