I'm outside the loop so please forgive me, but what is different between substack and a self managed mailing list?
I've been subscribed to a few website/blogs newsletters for years and they appear to work fine, and I think the owners are not particularly technical, there's WordPress plugins.
Substack is trying to turn itself into a social network, so comments on substack posts by other substack bloggers let people find other blogs. This is why half the comments on popular substacks are from other bloggers casually mentioning the articles they wrote.
It also means that if you comment on a substack, other people can find all the comments you made on every substack, by default.
I've been subscribed to a few website/blogs newsletters for years and they appear to work fine, and I think the owners are not particularly technical, there's WordPress plugins.