I have a cheap disposable bladed straight which I started with and still often use when in a rush. IME it only enforces good things, like confidence in applying the blade to your face and using a super light touch due to the ferrociousness of the edge.
The angle thing is a bit of a non-issue as the angle always varies depending on which bit of your face you are shaving and the direction of the hair growth. It's not so much learning fixed correct angles as it is learning how to find the correct angle and adjust during the stroke.

Just my thoughts on it. Feel free to shoot me down if you disagree.