Google's captcha system is overkill for most websites. If I want to filter out bad actors (on a simple straight-forward site), there are other more simpler and easier to solve captcha systems out there. They might not have the rigour of Google's system, but they do the job, and well.
I would however use Google's system if the site is massive and there is the possibility that someone is using a script or some program to algorithmically bypass the (simple) captcha, and register accounts en-masse and trying to create a psyop[0], or disinformation campaign, or even a sockpuppet army.
[0] https://en.wikipedia.org/wiki/Psychological_Operations_(Unit...