This post hits close for me as I am in the process of adding a couple of subscription-only features to my free app Quit That!. I'm starting off with adding passcode/Face ID security. I'm also adding notifications. Both will be behind a subscription wall. If you don't want to subscribe, the app will still function as it always has with all the same features and no ads. Who wants to bet I get reviews and emails about how greedy I am. 🤷♂️
I don't have the answer to this problem. When app users are conditioned to devalue apps to the point where they are not worth making (see Marco's Twitter comment in this post) things have gone down a road that's difficult to change.
Comment: Are app subscriptions fair to users and developers? by Bradley Chambers