It's not just that you need to get used to gestures, it's that they are not discoverable at all, and that they can be awkward to perform with mobility issues, old hands, short fingers, etc. It's easy to make the wrong gesture, eg. the phone detects a swipe down instead of left to right, more so if you are holding it in one hand, so it's finicky and frustrating to have to rely on it as the only way of doing a common action. Why is it so wrong to have a simple navigation bar, it doesn't take up any more space than the hideous notch at the top?