Absolutely, authors are loving substack, and it looks like Medium is still hanging around, but I would say that Substack is not censorship resistant, they've removed content in the past

https://edition.cnn.com/2024/01/09/tech/substack-removes-newsletters-for-pro-nazi-content/index.html

And the fees for your readers/you is 18% to use the platform, that's pretty steep and you're leaving money on the table 

https://support.substack.com/hc/en-us/articles/360037607131-How-much-does-Substack-cost