Not sure why thats the case for you. I'm on Vodafone/Kabel Deutschland too and got full ipv4/ipv6 dual stack? Is that one of those regional limitations that Vodafone seems to have?
Oftentimes you can just ask the customer service of Vodafone. If you reach a good agent, they will switch you away from CGNAT and you get a proper /56 public routable prefix on your cable line. Also works great for me. Be aware, the Vodafone modem won‘t forward the prefix for you. Use a Fritzbox or one of the other few cable modems where you get full control.
You are sure you are not behind a CGNAT? From what I’ve heard, that’s the case for everyone with IPv6.