So a lot of Java hate I think is mostly in jest.

Personally, Java was the programming language that I had to use for my first two years of college. It's how I learned OOP, data structures, and algorithms. I had to use Eclipse, which at the time was AWFUL (and maybe still is, no idea). I remember it being semi-normal for it to take over a minute to launch on my (gaming) PC.

Later on, as I learned other languages and got a job, I just haven't really had a reason to go back to Java, and most of my memories of it are from being annoyed at Eclipse and needing to implement Quicksort in it. I'm sure it's a great language and I bet it's a lot better and more convenient now. It's just kinda trendy and weirdly nostalgic to hate on it in a half-serious way :) .