Entering Lama Ruins
It wasn't easy to keep reinventing one's self.
It was difficult for the individual as well as for those around him. Steve couldn't employ Eren in normal battle tactics anymore because of his experiments. And nobody had the right or the guts to tell Eren otherwise.
Therefore, Eren's team members started keeping a safe distance from him.
They didn't want to get involved in his experiments and suffer the consequences. After all, they didn't have the convenience to heal themselves using their Ability.
Ana would have been overworked to death if everybody kept acting like Eren mid-battle. That too, when the stakes were this high. The rest of the White Raven crew members neither had the guts nor the privilege to try something as crazy as what Eren was doing.
Eren's killing efficiency had dropped way down from its usual level at the beginning. However, he quickly recovered all of it for the most part in relatively no time at all.