Sexual reproduction can remove bad mutations. Imagine two parents. One has bad mutations m1. Other has bad mutation m2. They have three children. The first gets only m2. The second gets both and dies. The third inherits neither.
Even though neither parent was fully healthy, one of the children was. Asexual reproduction cannot do this.
Even though neither parent was fully healthy, one of the children was. Asexual reproduction cannot do this.