Turn the question around. Bitcoin has been around for 15 yrs now and still has no legitimate use. Good tech doesn't take decades to find a use case.

SendGrid or Mailjet. Both have free plans.

I'd argue that most block lists target people who are openly hostile to marginalized communities. If you're in one of those communities, there's no reason to engage with those people and a lot to be gained by preemptively blocking them.

When Bluesky crossed the 10M user mark, they temporarily added a feature that showed it to you.