Substack gives a really nice exposure though, unlike medium and other platforms.

It's very hard to gain readers now on independent websites. Google search is dead (very few people now search for tech content), social media platforms penalize you for posting links and so on.

You can get a few thousand subscribers on Substack just by being consistent and interacting with other people. Now try gaining 1000 subscribers to an e-mail newsletter or RSS from your personal blog. People who tried it know that 5,000 views on your blog can convert to a few subscribers, and you need to get those 5000 somehow first.

A lot of people just repost their articles to substack for a reason. It's not forbidden. You can repost them from your personal blog.

Not true. Ghost sites grow quite well and much of Substack's network effects don't turn into real subscribers