Many many blended families are not only happy - but massively grateful for the huge difference a new partnership/marriage has bought to their lives. One of my closest friends lived a horrific life of physical violence towards both her and her children from her alcoholic husband and their biological father. As well as grinding poverty.
Her new blended family has taught the children what a real father is like and modelled the essential ingredients of a loving, kind and dependable spouse for the children to learn what a real partnership should be.
This all sounds lovely, but you talk solely about fatherhood and modelling a decent marriage ie. it's all about the relationship between the children and their new stepfather, and between this woman and her second husband you don't mention the quality of the relationship between the children and their stepsiblings, if any.
The enforced proximity to stepsiblings is the problematic element for many children in blended families, who find themselves sharing a house and one parent with other children, whom they may like or dislike, but are thrown together with purely because their parents are in a relationship.
I mean, even if you were happy you no longer had to live with your alcoholic biological father, would you necessarily think that a nice stepfather and your mother's happiness was compensation for sharing a home with his children?
Because I know what I would have thought aged eight, or thirteen.