Well, there are many types of work harmful to society that people partake in. Coal, content makers for abusive social media, there have even been some organizations in history which have committed atrocious war crimes in which people had jobs, and they would have needed to re-specialize had they lost those jobs. It's not that there is a lack of sympathy for anyone who loses their job, but some organizations and efforts are harmful to the broader public.
The "HN and other Tech elitists" don't like social media because it's harmful to society. In the 18th century, Immanuel Kant already brought forward the notion that it is immoral to use a rational human as means to an end. We have broadly accepted this philosophy in life. So when social media companies exploit human attention and cause significant harm to their mental health as means to achieve advertising income and towards mercenary surveillance (surveilling the public for the highest bidder), that is broadly considered questionable. And not only by HN, but by psychiatrists, psychologists, other health care workers, teachers, social sciences researchers, and so on.
There is a national security argument to be made for TikTok as well, which is why governments have taken an interest in it recently. So the ends may be more insidious than advertisement and mercenary surveillance like we see across all social media.
We know that the content on TikTok changed a lot the day Russian invaded Ukraine, there has been a flood of misleading information about the war, including a wave of glorifying the "Z" armed forces and the "special operation", not to mention the "denazifying" stuff. People are being used as means to information warfare ends, too. And by both sides of various conflicts. This is also, arguably, immoral. Although I doubt there's much of an argument to be had.
The mental health and the national security arguments are separate, but given their context, characterizing this as a hate for mom and pop shop closures in some way or form is inappropriate. I think this comparison is a bit of a low effort troll. It's clear you want to rile people up as I don't think anyone starts a serious discussion by calling the other party an elitist or any -ist. But still, above are the reasons why very many people dislike social media and TikTok.