Actually, it’s one of the best-designed screens, and I’ll tell you why.
1. The huge time display is doing some heavy lifting because when the alarm wakes you up, your eyes are not fully open, so having it big makes sense. You can try squinting your eyes and see which version is easier to read. There’s also another reason for this, which I’ll touch on in my second point.
2. The dark background is there for a reason. Do you know how annoying it is to see a bright screen the moment you open your eyes? You don’t want that. Plus, it gives the best contrast with the numbers, making them easier to see immediately.
3. The buttons are also big because you’re most likely going to be clumsy since you’re not fully awake, so we need to make it easy for you to make a decision.
Now, why is Snooze the primary CTA? First of all, the likelihood of you pressing that is higher when you’re deep in sleep. Remember, you’re not fully awake, so your brain is slower at processing information. It naturally defaults to the path with the least resistance, which is the Snooze button. Funny enough, this will save you on many occasions where your brain is just telling you to stop the noise, even though there’s work or something important you need to attend to.
Now, the Stop Alarm being a slider is for two reasons. First of all, it’s a very critical action because you might miss something important if you accidentally touch it. Second, the brain power required to use the slider means you have to be almost fully awake to complete the action.
P.S. With improvements to the contrast, I think the Snooze CTA could work better as black text on an orange background.
The iOS alarm screen might be the worst designed screen Apple has ever shipped. Everything feels off - the clock, the buttons, the controls.
Here's my attempt at fixing it - (thread)