Issues with CAPTCHA:
- reCAPTCHA v3 detects unusual user patterns. Guess what... some screenreader users navigate in a certain way and get flagged as bots
- Puzzles, simple mathematical or other simple tasks can still be hard for people with language, learning or cognitive disabilities.
- Privacy when using, for example, Google's CAPTCHA is at stake.
- Recognizing US store windows, fire hydrants and crosswalks is hard while they look different in other countries.
- No alternative for image text recognition which are most of the time hard to read for sighted people..
- No control over code when using external CAPTCHA tools.
- (Googles') CAPTCHA is brought to you in a language that might be not the language of the website. You can not control it.
- No control over color contrast issues and other issues. Sometimes it takes long to have these issues solved.
- No CAPTCHA.
- Honeypots (here is what W3C says about honeypots)