There's also an age effect. If you're maintaining a Delphi or VB or PHP codebase now, you're probably working on an older system, which means you spend a lot of time stepping on rakes that someone left in the code ten years ago. If you're writing something in Elm, it can't be more than a couple of years old, and you're probably still in the green-field honeymoon period.

This emotional response probably transfers onto the languages themselves, which means any language in decline will naturally attract resentment.

If someone to dislike a programming language, they have usually been exposed to a codebase written it. Very few dislike something they have never encountered. That means that the language must have been popular at least at some point if a large number of people dislike it. That may either be because it is no longer considered modern (e.g. Fortran, Cobol) or different communities are split in their view for some reason (PHP, Visual basic).

I would say a language has to be popular to be disliked. That rust and kotlin score so low on the dislike-scale could be because people love it but probably also because the rest wouldn't consider it. If a language is used by few, there's no real reason to dislike it.

At least that's the case for me. I can say that I dislike PHP because I used it in the past. I couldn't say the same about rust.