The reality is, very few is 100% stable in all those aspects you mentioned. There are people who are willing to try to become great parents despite their shortcomings. Parenting is about learning, it has no handbook. But I agree with your opinion if those individuals are ones that always get into trouble, abusive or are mentally unfit.

totally get your point but I think most parents arent stable in one aspect you mention but still turn out to be great parents. which make it more beautiful because they were able to overcome their weakness because of their love for their child. and as a christian, it takes faith in God that we will be able to raise a child despite of knowing your flaws and short comings. well these are just my thoughts…