I agree that appearing as dog poop and video conferencing is appealing to 5 year olds. But I disagree with your implication that no one over that age would find appearing as dog poop or video conferencing appealing. We all know that a lot of older children, young adults and even elders like childish things and find them appealing. Witness the current glut of childish and whimsical unicorn items are selling to people of all ages, not just 5 year olds.
You may think they shouldn't appeal to anyone over 5...but they do.
But even these appeal only to those between 5 and 15...that's not necessarily a mistake on Apple's part. I was in a car once with a mom and her 10 year old, who was on an iPhone. Mom's iPhone kept making this "ding" noise. I asked her what it was. "Every time my daughter buys someone on the iTunes store, it rings..." So if silly, stupid, childish things like appearing as dog poop and video conferencing can get kids to use iPhones--and from there buy silly, stupid, childish music, apps and games from Apple's online stores, then I'd say Apple DOES know what it's doing.
I was not saying that VC is not appealing, actually it is my field, 20 years now doing this professionally. I am just so unimpressed by their implementation, now that they finally got to multiparty conference they did such a terrible job. Maybe I am biased because I am a PRO in this field so instead of saying that they do not really have people who understand the matter I try to justify it. Moreover the fact that older phones cannot join a multiparty call that is bizarre too, it could show the active speaker at least but I am digressing.