I already feel like the infants and toddlers are redundant, especially since we still have a baby stage. It's just way too much to play out just to get to childhood. I don't need every single phase of infancy and childhood before Sims finally grow up. I think Sims 2 had the best general idea for life stages, except for young adults being tied to University. Although I personally love the older teens in Sims 4 because they can be more independent and wear anything in CAS that older Sims can wear. But had they been just a little shorter, they would have been more visually distinctive.
Also, the restriction of 8 Sims to a household including pets would make playing families more complicated the more life stages there are.