This is Googles captcha system and its used by a bunch of services. It has nothing to do with Mailchimp (except that they use reCAPTCHA) so changing mailing list provider for this might not be a wise idea.
With that said, I much rather prefer this new reCAPTCHA compared to their old version with hardly any readable characters.
With that said, I much rather prefer this new reCAPTCHA compared to their old version with hardly any readable characters.