Basically. There is no incentive to charge a one-time fee when you could make a lot more money on in-app purchases. I think you will start to see a shift in how apps work over the next year or so. One-time app purchases aren't typically very sustainable for the developer, which is why you are starting to see app subscriptions pop up. Plus, the Apple announcement of reducing the cut they take with a yearly subscription will likely accelerate the process.
I'm curious if a subscription based mobile game would work. I'm guessing there would be way more failures than successes as I doubt most people would want to pay. For Clash Royale, let's say the game stays as is for free, but for $1.99 per month subscription you got double the chest storage, half the time unlocking, and a guaranteed legendary per month (weighted to one you do not have, or less of). I wonder if people would jump on that. They could still have Gems/Chests for those that really wanted to accelerate their progress.