Somehow it's really hard to find numbers, but AFAIK at least Telekom and 1&1 don't use CGNAT for home connections, which already rules out that 77% have it.
I'm less sure about Telekom. For obvious reasons, it's hard to find info in English.
My anecdata is that I'm on 1&1 fiber and I have a public IPv4 address.
German ISPs commonly seem to have an option of their "old" platform (v4 only, no v6) or their "new" one (v6 and CGNATed v4). Maybe you're on their old one? Or maybe they only use it for certain account tiers or somesuch.
I've been with 1&1 for a long time, previously DSL and VDSL, so I could have something grandfathered in - but I doubt it. Especially after the recent transition to fiber. And I am not paying for any special options.