Nobody has mentioned the similarity between RG and Wimbledon. In both cases, Maria was the favorite, not to say the super favorite. Li Na and Kvit were pretty unknown in Grand Slams. Li had played the AO final earlier this year and Kvit the semis at Wimbledon last year but who could have predicted them to outplay Maria? Every journalist wrote Maria would play the final in Paris and could win over Schiavone. For Wimbly, everyone already saw Maria lift the trophy. Actually Maria was dominated by both Li and Kvit and lost in straight sets.
None of these two players are superior to Maria. They don't have Maria's experience. But they played very smart. Not a great tennis, but a clever tennis to exploit the opponent's weaknesses.
For me this is a very big disapointment. For any random player, playing the semis at RG and the final at Wimbledon would be a big achievement. Even Wozniacki would have loved to get to that. But Maria is NOT a random player. Now I am wondering about her chances to win a GS in a future. She improved a lot since her coming back from injury. Is it enought to win another GS?
One of her problems (there are many) is her serve. Actually she doesn't have the same powerful and accurate serve she had before the shrould injury. Someone in this forum said earlier that serves are not that important. I disagree. Big serve is not the only thing a champion needs. Every champion has a big serve. Maria won three GS thanks partly to her serve. In modern tennis, a big serve is necessary to win the games, especially for female players because they are supposed not to serve well. Look at the men; they all have big serves. Kvitova serves great too, even her second serve is good to distabilize Maria.
Many mention again and again the shoulder injury to justify the defeat. Well the injury is 3 years ago. She didn't come back yesterday either. So we have to look at other reasons.
I always think the future of female tennis is not only in hard hitting. Big hitters like Azarenka or Wozniacki can go far, but it's not enough to win a GS. Playing clever is quite essential to become a true champion. Kvit's coach, Kotyza, said during a post-match interview "Her [Kvit] brain is a big advantage for this game.". He's not wrong.
Now what can we advise Maria's staff? Improve more and more her serve as she already did a lot, work on her fitness (Philli would say her stamina), adapt her game to the new generation of players, and of course play more with her head as well as her arms.