For consumer traffic, your probably right. In data centers, cloud computing, and various enterprise networking solutions, IPv4 is still king. I'm sure IPv6 would work fine in all these use cases, but as long as many large tech companies are not exhausting the CIDR ranges they own (or can opt for using private ranges) there is no impetus to rework existing network infrastructure.
The underlay might be v6, but that doesn’t change the fact that people heavily use v4 for the actual workload traffic (i.e. the cloud computing part). EC2 VPCs still default to v4 only last time I checked.
