Some thoughts on this:

1. I agree Barbie is primarily for nostalgic adults rather than child audiences, though I still think children will enjoy it.

2. I completely disagree with the idea that death isn't an appropriate subject for children's stories. Children are as likely as anyone to encounter death, and stories dealing with it can and do prove cathartic and empowering for those faced with it (I can tell you that from personal experience). It also provides important lessons about life's realities. Yes, children don't need to dwell on death all the time, and there are ways to tackle the subject in an age appropriate way, but to say death is an off-limits subject for children is a view I profoundly take issue with (I know that's not exactly what you're saying here, but you'd be surprised how many people I've met who think that).

It's also worth remembering children aren't a Borg-like homogenous collective who all react in the same way. Proper consideration should be taken for different personalities, temperaments, and so forth. As such, parents know their children best, and are best equipped to decide at what age their charges should read or see the likes of Watership Down, Bambi, A Monster Calls, Charlotte's Web, the Harry Potter novels, and countless other classic children's stories dealing with death.

In fact, I don't believe any subject should be off limits for children. More of my thoughts on that here, if you're interested. :)

https://writingcooperative.com/not-suitable-for-grown-ups-c930de1c0635