Release the button; iPhone will then take the photo.
Another simple way to take better photos of moving subjects is to keep the screen still as much as possible. You should avoid movement as much as possible when taking photos and this will help a lot.
The best way to keep the screen from moving too much is to bring the phone closer to your body. I find this especially effective in cold weather when your body tends to move more. You can also wait a few seconds before taking the photo to steady yourself.
A particularly common mistake is taking photos too quickly. When you take a photo in a moment of excitement, there is a risk of the photo being blurred. So you should wait and observe before taking a shot (unless it's truly a once-in-a-lifetime photo opportunity).
If you see a scene that looks particularly interesting, such as a street photography background, take a few minutes to look around and think about anything else you might want to include. The end result will be more interesting.
Another way to take better photos of moving objects on a smartphone is to zoom out. For example, on an iPhone, it's recommended to take a photo at 0.5x zoom if it's a fast-moving subject. Creating distance, as mentioned earlier, will also help significantly. You can crop the photo later if needed.
Taking photos of moving objects on a smartphone will require more effort and thought, but it's not impossible. You can take better photos by downloading apps that control shutter speed, but even in smartphones, you still have options. For example, if your device has a continuous shooting option, you should use it.