My verdict: the platform that made newsletters cool again.
Substack succeeded where others failed: making writing accessible AND monetizable for independents. Free to start, 10% only if you make money. Perfect alignment. For creators who want to focus on content, not technology, it's unbeatable. The platform to launch your newsletter and monetize it. Substack lets you publish for free or paid (subscriptions). The interface is simple, the editor is pleasant, and distribution is built-in. Substack takes 10% of paid revenue. Ideal for writers/creators who want to monetize their audience. SEO is limited and you don't really own your audience (emails are with Substack). But it's the simplest to get started.
What I like less: limited design customization, SEO not optimized (your articles stay on Substack), 10% on revenue can become significant at scale, less control over your audience than with a self-hosted tool.
My advice: perfect to validate a newsletter idea without investment. If you take off, you can always migrate to a custom solution later.