Cloudflare sees over 40%, and it hasn't gone up in the last year even with the overall traffic increase. Personally, as the APNIC article also says about their own observations, I guess the overall adoption is somewhere in between.
https://radar.cloudflare.com/adoption-and-usage#ipv4-vs-ipv6
But we have to remember that this reflects the adoption on the client side. With many high profile services still IPv4-only, the fraction of IPv6 flowing on the public Internet might be much lower.
I wonder what incentives are needed to push this forward, because it's not the same incentives as years ago for sure. We've long since exhausted new IPv4 allocations.
If we're looking at the portion of traffic, most of the big bandwidth heavy services (the video streaming sites and CDNs) are on IPv6, the long tail of IPv4-only services tend to be lower bandwidth stuff.
I believe one big anti-incentive is rate limiting, especially nowadays. With IPv4 getting a range ban is somewhat effective, way less effective on ipv6 (theres a reason HE tunnelbroker is marked bad nowadays, discord bots doing music load balance over ips on tunnelbroker for pulling youtube audio data.. they ban a /64 but you balance over a /48 or bigger). I believe this was the main reason Discord disabled IPv6 (not sure if thats still the case, but it was back in the day since bans and api rate limiting was ip based).