There are several things that are often shown when a writer shows a utopian future, several things that sound good but just don’t work.

The first is population. Often you see the earth with a much lower population. Humans are like water, we tend to fill any container we are in. Once you start to eliminate the reasons for having small number of kids a great many people will start to have more.
The main limiting factors for how many kids people have are time and money. If your in a future where the money needed to support you and your family takes little time to get then you would have as large of a family as you want.
If even things like daycare are cheap then I would think you would start to see larger families, not smaller ones.

The second is lack of crime. While true, if poverty was a thing of the past crime would plummet, but it will never go away. You will always have people looking for a thrill, or who would rather steal then earn luxuries.

Third is money. I know I have said it before, but I can’t see any way for humans to live without some form of money. Every time I see a plan for it it’s either just another name for money.