Unfortunately, once you share something online it's moved beyond anyone's control. Even if the platform respects your wishes and does everything right, there's always 3rd party web crawlers, data harvesters, archival services, etc. They are always around, busily vacuuming up everything they can on the web. Few if any shared posts or comments will ever be truly deleted. Storage of text is cheap, and a lot of entities love hoarding data.
So, try to only post stuff you wouldn't mind your parents, coworkers, friends, etc. knowing about. Corporations and governments are moving more and more towards 100% surveillance and away from privacy and anonymity. It's a giant problem, and I hate it. But the only element of this you can control is your own behavior.
I agree with you. However, in part this is often done because giving or receiving medical advice online is generally ill advised. There can, in theory, even be legal concerns (potentially). Say someone gives bad advice and the person is harmed from it. I also think that all the misinformation that got disseminated during the pandemic left people gun-shy on these topics.
But I still agree with you in spirit. The "talk to your doctor" thing can be a too cold and reflexive with some folks. And there are a few home remedies that do work. And maybe the person asking just wants some emotional support and not the usual soulless canned advice.
This topic reminds me of people who automatically throw an 800 number out there whenever certain key words get mentioned. There's almost always good intentions behind that. But in the USA at least, calling such a number can make a person's life much worse. Loss of agency followed by a huge medical bill. Because it's not really about helping the person. It's about optics and collecting money.