based
image:
screenshot of a Tweet from Running With Scissors reading
"We've been told our games are too expensive in some countries but we've been using Steam's recommended pricing for a while. We trust Valve enough to not change this. If our games are still too expensive for you, you can pirate them until you have enough to support us."
My understanding of "based" from years and years ago was that it was used as an exclamation when people essentially weren't afraid to speak their minds even if they're likely to get shit for said opinion.
That's why it's gotten associated with the alt-right because it was usually bigoted douchebags saying bigoted shit that other bigots would then respond "based" to. I feel like the terminology was associated with 4chan in its early usage and spread to reddit.
I believe your definition that is popular with Gen Z is a newer development.