I find it to be very mean-spirited as well and going as far as linking the deletion of the site is pretty harsh and unneeded. That said, I kinda get the "clogging up" concerns. As a website owner and someone who binges the small web frequently, content-less websites aren't something I enjoy exploring. I want to discover something, no matter what it is. If a site has zero reasoning or features something like a social linktree, browsing becomes a bit frustrating over time.
What's actually "useless" is hard to define. But generally speaking, low content sites are a bit of a grey area. Can be cool and fun, can be a waste of space. Depends on the case.