that was 30 years ago? New Java developers have been born after the original inception and learned the language long after. Reputations change over time.
Core Java was staunchly against incorporating any functional features while the rest of the ecosystem was innovating
Sure, because Java isn't a functional language. Taking a wait-and-see approach to whether the style of programming will be a fad is defensible choice when you have to support it forever. And it kind of was a fad. The only thing that really came of it in most mainstream langages is passing functions as arguments. I've yet to encounter a code-base in the wild that's actually functional.
What does functional mean to you? From my POV I see lots of features in Java coming from the functional programming world, but perhaps I have a different understanding of the term to what you do.
Core Java was staunchly against incorporating any functional features while the rest of the ecosystem was innovating