You misunderstand.

The concerns about the "processing cost of NAT" were edge concerns. Companies, homes, edge-devices with 100 or 1000 RFC1918 addressed devices behind them. When ipv6 was created, NAT wasn't a thing, as processing power just wasn't there.

And it was thought the processing power would never be there.

Yet now everyone has NAT in little devices at home. So the need to route 100 IPs into every person's home isn't a thing. Which is inline with my comment about how the world looked different 30 years ago, and how the concept of "IPs for everything" is the reverse of what people even want now.