Well, people have stopped using it literally, so I don't see what it can be except a pejorative for subjectively "old" people, usually. If you actually argue that people younger than about 55 aren't boomers, you'll just be told that's not what the word means any more.

If you are a boomer, then I agree, why should you feel insulted?

Almost every case I've seen has used the word in a dismissive, ageist fashion. I think it's similar to mild ethnic slurs like "yank", "limey", "frog", where the target has similar or higher status.

At best it is lazy writing, and most commenters on HN write better than this.

See https://en.wikipedia.org/wiki/OK_boomer