Shang Chi was one of the best received post endgame movies, the fans seemed to like both him and the movie, and it kind of prepared the ground for a possible sequel. He was a perfect character to get the old heroes treatment (like Cap, IronMan and Thor) both individual saga and Avengers movie. However, we never got to see him again until Avengers Doomsday.
Was Marvel Studios' original plan to not use Shang Chi until the next Avengers movie or was it a consecuence of the whole Simu Liu-China problem?