There again, you’re going past the text to a darker place than what it actually presents. There is nothing about abandoning people who aren’t “perfect specimens” at birth. That’s literally just something you’re adding to it all on your own.
And again, they don’t kill them off. They leave them behind. I doubt they leave them naked and weaponless.
Being too badly injured to keep up, or for the tribe to wait for you to heal, is a likely source of adventuring backgrounds.
I am going a bit beyond the text, but unduly so.
If, for example, the tribe is willing to leave behind an adult warrior, one who fought hard for the tribe and was injured badly enough they could not keep up, what would they do to a child born with a club foot who will never be able to keep up? A child of ten who catches an illness and can't keep up, why would they be treated with more care than a great warrior who needs only a few days extra healing?
I'm going beyond the text, but not beyond the logic of the text. Those who cannot keep up are left behind. Those left behind are left behind because the tribe lives in a harsh and dangerous environment that could kill the tribe if they allowed the weak to stay.
Sure, maybe the injured warrior or whomever is left behind is aware of the settlements in the lowlands. Maybe coming from a society that fears age and weakness more than death they might flee the mountains and seek shelter out of fear for their lives. It is possible they survive the journey, which could be a week or more travel, alone in the mountains, trying to hunt while injured. But the chances are thin, and more than likely they will die.
Now, I'm not saying that Goliaths have to be this way. I'm not even saying I want them this way. I completely threw out this entire section of their personality when I put them in my games, because I don't like it. But, this is a completely valid and supported view of their RAW, and acknowledging that is important I think. Because I know personally that this part of the lore is a reason I never was much interested in Goliaths to begin with.
For a similar example, in FR I
HATE Sune, the goddess of beauty. Because part of her official dogma is that being beautiful on the outside is the most important judge of whether or not something is good. Ugly things are bad, beautiful things are good. This outlook is one I could never agree with, it is a repulsive philosophy. Now, if I was roped into running an FR game, I would change it, because a Goddess of Beauty does not need to have this outlook, there are ways to make beauty a philosophy that is less repulsive. But, I think acknowledging that the RAW states what it states is important if you are going to be talking about reasons people might like or dislike something, and what should be changed.
That's part of why I'm doubling down as you guys keep telling me I'm exaggerating what the Goliath lore says. I'm not exaggerating it. I'm following it into aspects they don't directly state to be sure, but Goliaths are the only playable race, and I'm including orcs and lizardfolk in this, that specifically state that they abandon those who cannot keep up, and seek death to avoid getting old. That means, even orcs, which people are saying they don't like because of how dark they are, take better care of the elderly and injured in their tribes than Goliaths do. Because, while we can assume what might happen to orcs, Goliaths state it as a fact.