I think that GT Sport needs, desperately is a proper tutorial and guide system.
I'm thinking like the Lewis hot-laps series, but far more in depth and for every single race-car car in the game. They can use real drivers or just really good sim-drivers, have them break down the characteristics of each car (say GR3 for example) and then use a couple of very different tracks to give examples, of how the cars behave and how to deal with this.
For example, with the Audi GT3 that I race, I really struggle with low speed grip. Having someone with more experience and more ability explain how I can deal with this better than I am would be a huge help and I'd get more enjoyment out of the game.