It's not a weakness thing, it's about learning how to drive a sim. If you try to follow the line on screen, you;ll never learn how to really drive a racing line. Because of slip angle, you can't turn in or track out where the line actually is- you turn in early, the momentum of the car brings you onto that line but your car is not quite pointing in that direction (the amount depends on the car and tires). So though a dynamic line (I assume you mean that painted line through corners) can give you an idea of how to take the corner, it's a bad crutch to use.
Also, that line will change according to the car and tires you are using and so the line painted on the corner is only accurate for one car and tire or at best one class of car. Every other different type of car and tire combo will have a slightly different line and so you will most likely always be racing on the wrong line. There is a huge difference between types of cars- open wheel, low DF, high DF, GT, retro high power, modern muscle, slicks, street tires etc. The line is different for all of them.
The other problem is that someone worse at racing than you are may have decided where that line should be. A human determined where that path for that line should be and though it can be assumed the person is a knowledgeable as a game dev who is familiar with the game, you can never get better than the dude who painted that line on if you don't find your own way around.
