There is a lot of projection in that comment. Maybe there were a few anti-boomer memes before this post in your feed which led you to it.
The website shows death statistics of every generation with people alive, famous people and animals. The title of this post just points out that exactly a third of the boomer generation has now died, which is a mildly interesting threshold, hence the community this is posted in.
This is a neutral post and it isn’t anti-boomer per se.