You’re overlooking the fact that these apps don’t cost these people more than their time to maintain. They don’t have hosting costs. The costs are literally the devs time, that’s it.
Would they make less money going subscription only? Absolutely. Would they lose money? Absolutely not. Completely removing the app means they make even less money - $0 in fact.
Most of these apps already had subscriptions. It would be a config value or database change to update the price for new subscriptions, and one line of code to only allow users that have a subscription to use the app.
Also if your entire livelihood relies on making your entire business off the back of a free api to someone else’s business, you can’t complain. When this happens. Your business model is bad, and then cutting off your access is a known risk.