In reality, losing the nsfw content was certain death, but losing the app would have just been a downsizing. Maybe not even a major one - platforms are sticky as hell. I think most people would happily use the browser.

Now if you go out of your way to make your browser experience dogshit, like Patreon... Then yeah, losing the app store is very bad.

That would make sense if apps like Twitter or Reddit were banned from the app store or had also decided to ban NSFW content, but they seem to be getting along fine with their verification-free "click here if you're an adult" systems. Why was Tumblr different?

To be sure, this move by Discord seems like a reflection of the same kind of decision that Tumblr made. But blaming it on the app store in Tumblr's case doesn't seem to make sense. Discord seems to be doing it either to comply with increasingly fragmented laws, out of actual moral desire to fix a problem, or to avoid lawsuits-- not because of app store policies.