I think it's a fact of life. Sunlight is extraordinarily bright so phone screens would have to be retina searingly bright to outshine it in all circumstances.
Early cameras had the equivalent of a screen for viewing which only had the lens between it and the subject, so you would think it would be plenty bright, but they had to use a hood in order to be able to see things. Later cameras use an eyepiece which has a similar effect.
Unless you can somehow shield your screen, you're going to have issues. I'm sure you could McGyver something together to go around the screen to minimise glare, but short of adding a hood, it's never going to be 100%.