I should probably have written a lot more than one sentence there. You're absolutely right about the benefits of meeting randoms on the internet, and clearly it still happens and works for some people. But it always did have social scaling issues - as a particular system or chatroom got more popular the success rate fell. I also worry that the culture has changed. "On the internet" really isn't a place apart from everyday life now, and we have a giant all-encompassing social network. And a dating app.

As one of the sibling comments points out, once such a system becomes popular it's also going to be a target for spammers. If there have been any advances in chatbot AI over the past couple of decades that is also likely to make the problem worse.