The important point is that, if you’re able to readily switch to a different app when your current one changes its payment model, then… do it. Just vote with your wallet, and don’t worry about it. To write a pissy review of an app you liked yesterday, in an attempt to vengefully damage their business, is pretty reprehensible, right? It’s like giving one star on Amazon because the delivery was late. Don’t be a child. Move on.
See also his rules for deciding on whether a subscription is worth it on an app by app basis. I love subscriptions, but only for the apps I get the most use out of. I don’t pay for a lot of apps because I don’t need or use them. I’d love for others to be subscription so I can more readily try them out, without feeling like I pissed away $20 on something which ultimately didn’t work out.