I mean, that just isn't true. There are amazon tribes today where they just send them down the river to die... your ideas are a disney-fied version of a false past that never existed.
Yes, humanity is full of various societies that do things differently. These ideas aren't disney-fied - they're just accurate representations of the fact that people care for each other, most of the time.
I appreciate your anecdote, but here's a few counter-examples:
Unspecified Amazon tribes don't represent the lion's share of historical treatment of aging populations. One negative example doesn't undermine the point.