Actually plenty of physical traits occur with no evolutionary benefit because the genes have been introduced to the gene pool but have not yet been eliminated from it
That takes a long time
And someone could have beneficial genes along with bad genes
So genes do not get completely eliminated like that
What is the evolutionary advantage of all the genetic disorders Ashkenazi Jews have
Based on your logic those genes would not exist if they did not have a advantage
Supposedly simply not being anonymous in donation greatly increases your chance of being selected
Supposedly a lot of men are only willing to do anonymous donation
Personally I think simply to prevent incest their should be no anonymous sperm donation
The problem is those child custody laws prompt men to choose anonymous donation
Also it might be better if people just reproduce from donation so men stop fighting over women and trying to please women