Exaclty my point of view! While you try to race in single race, starting from last, and overtaking everyone in T1, crashing into others cars (as they all are AI) and restarting after you spin out of track, you may never learn how to really race at propper manners. I do like the MP with ranking system as in IRacing/ACC, because if you spin out, there is no reset button, you need to recover your position, and others drivers may do the same (go off track, spin etc), and its possible to recover your position, something that doens't happen very offten with any AI. Also, if you have something to lose, like a rating, you wont try to do risk moves that can end your race and end the race for others drivers in one move. You need to learn how to be patient, wait for the opportunity to overtake, learn how to be fast and consistent without make mistakes, because there is no reset button. An AI doenst had the unpredictable from the human behavior, to defend a position, to force you to make a mistake, or to trick you pretending that going to overtake just for you make a mistake, and others. Even F1 2020 which had one of the best AI IMHO, doenst give so much pleasure as race against others drivers.