It contributes to it, because now you're behind the same public IP address as X other people. You're then X-times more likely to get flagged as suspicious and need to enter a CAPTCHA X-times more frequently.

Cloudflare easily detects that using your discrete external port range and knows better than to show you a CAPTCHA.

Anecdotal experience (I know, of course... this is sample size n=1) tells me that you can't be further from the truth.

Putting CF aside, anyone who has tried to edit Wikipedia anonymously should understand the pain of CGNAT.

Someone should tell Cloudflare that because it's not been my experience at all.

(now n=2)

It's not a direct cause, but if an IP is hitting my website with spam, I don't care if it's a spam bot or a CGNAT exit point. The only way to stop the spam is to take action against the IP address. For CGNAT customers, that means extra CAPTCHAs or worse.

You can ask your ISP for your own IPv6 subnet if you don't want to be lumped in with the people whose computers and phones are part of a scraping/spamming botnet.