I would highly recommend the recent Freakonomics Radio series about whaling. It’s Episodes 549-551 and the bonus episode from 2023-08-06. If you’re firmly against killing any living creature (or at least sentient creatures), I highly doubt it will change your mind (and I don’t think that it should or that it tries to), but I also think it is really fascinating learning about the history of the whaling industry and hearing the perspective of a modern whaler in the bonus episode. Putting aside the obvious ethical issues with killing sentient creatures, it’s interesting to consider things like whether there’s a sustainable level of whaling, what a sustainable quota would look like, and how much we’re in competition with certain whale species for harvesting fish as food for our own species. I personally appreciated how unbiased Freakonomics tried to be in their discussion of the topic.
What you’re describing is only possible on de-anonymized platforms that essentially have “know your customer” type policies where users have to provide some kind of proof of their identity. While I agree that there is value in social spaces where everyone generally knows the people they’re interacting with are who they say they are, I don’t think this is ever going to be feasible in a federated social platform. I think Facebook is the closest thing we have to what you’re describing, to be honest, and I believe Meta has even kicked around having a more sandboxed Instagram for minors (though I don’t use Instagram, so I’m not certain on the details there).
For me, in most cases on a platform like Lemmy, a person’s age is not something I care about. I care about what people are sharing and saying. But then again, none of my interests for online discussion at this point in my life are really age centric. I think there are clearly better platforms than Lemmy if people want to guarantee they’re only interacting within their age specific peer groups.