Assuming MBTI is genetic? Do you think earth would fall apart with everyone having the same weaknesses, or do you think some people would develop different functions that are missing in order to survive?
Assuming MBTI is genetic, I expect we'd see the emergence of recessive genes after a generation or two. If you divided humanity into 16 sectors, it wouldn't hold up for more than a few years at best. Diversity is survival.
In response to the OP, I cannot say what 16 different worlds would be like, but I can share the experience of living in a household with 4 IFPs. Basically, everyone spun on their own orbit much of the time. Self-entertainment was the norm. Creative projects were embraced, though seldom finished. Individuals were subtly coerced into not following their genuine impulses to conform; instead the sentiment "Don't be like anyone else" was underhandedly demanded. Animals were a valued part of the family, and nature was respected. No one wanted to have their internal state altered, tempered, or even peered into.
I'd like to add something about peace, harmony, and gentleness...except as one of the "angry, oppositional" Fi-users, I more or less shattered the idyll with my flareups. So, living in INFP-land wouldn't necessarily be as serene as you might expect. Actually, it might be better to divide us into enneagram types, or tritypes, cause I was a LOT different from the other INFPs in my family, lol.