> Personal blogs are not necessarily self hosted. Substack is very popular and not uncommon nor dying.

That isn't necessarily quite as personal as a personal blog from the era I'm remembering, though. My impression is that Substack blogs (as well as similar sites like Medium) are typically used for content about particular topics, deliberately crafted to appeal to the interests of some audience. They're more akin to a newspaper column than a diary, if that comparison makes sense.

Some contemporary social media sites which operated on this model were LiveJournal and Xanga.