Disagree. If you've only got IPv4 experience and have a number of possibly legacy devices on your network, then there is a significant amount of learning and changes required to make it work with IPv6 (securely).

It's entirely reasonable to say "It works fine without [=zero business value], no need to invest that amount of work.". This makes IPv6 a negative value proposition for many orgs.

It depends on the context.

I mostly focus on users of VPN services. It's still rare for them to handle IPv6 traffic. So if you have IPv6 connectivity, IPv6 will leak, bypassing the VPN. Unless you have firewall rules, or disable IPv6 while using the VPN.