Email's been here for years. But the reason Substack wants you to call your creative work by their brand name is because they control your audience and distribution, and they want to own your content and voice, too. You may not think you care about that today, but you will when you see what they want to do with it.
I know you think you have control over your subscribers on Substack. But understand this: every single new feature Substack releases, from their social sharing to their mobile apps, is proprietary and locks you into their network. They don't let your writing live on your own website or domain under your control unless you pay them for the privilege. And it'd be a shame if something happened to those subscription dollars you're counting on, wouldn't it? Even when you say "but my readership is growing!" know that most new subscribers come from other writers referring their readers to you. Somehow... Substack wants credit for those writers making that choice? Even though it was your writing that inspired it? That's not some magical network effect thanks to Substack! That's just the internet, working as it was supposed to.
Links are powerful — that's why Instagram and Twitter and Threads punish and limit them, and why Substack tries to take credit for them. And that's why "wherever you get your podcasts" is such a radical concept — like email, it's a medium that the tech tycoons don't, and can't, own. People can read your writing "wherever they get their email".
We constrain our imaginations when we subordinate our creations to names owned by fascist tycoons. Imagine the author of a book telling people to "read my Amazon". A great director trying to promote their film by saying "click on my Max". That's how much they've pickled your brain when you refer to your own work and your own voice within the context of their walled garden. There is no such thing as "my Substack", there is only your writing, and a forever fight against the world of pure enshittification.
Substack is, just as a reminder, a political project made by extremists with a goal of normalizing a radical, hateful agenda by co-opting well-intentioned creators' work in service of cross-promoting attacks on the vulnerable.
Same for 'Medium dot com'. Another attempt at a walled garden for people's thoughts.