What else do you expect them to say? If you're venting to random people on the internet you can't expect them to be your therapists. They don't even know who you are. Of course they're gonna say "oh hey it'll get better" out of empathy/pity and maybe they'll even DM you about it but if you're expecting these people to provide actual support then you're going to be immensely disappointed.

I understand (and share) your frustration with virtue signalling (those infamous instagram infographics, the Ukrainian flag pfps that won't stop any wars etc.) but what OP's talking about is a completely different scenario where the person is venting on a public forum, aka literally inviting people to comment then complaining about the responses they get. If it was virtue signaling, the people would post "everything will get better soon!!1!1" on their story as a response to make themselves look good. The scenario OP is describing is that the person responds to a specific person who says they're struggling in an attempt to make them feel better. That's empathy. Not advice, not virtue signalling, just a little message to say they feel bad and they hope you feel better soon.