I think the idea here is that 1% of users with the shitty ISP is going to have a much worse experience than anyone was having with the captcha. This is super context-dependent, but being told I need to "contact an administrator" when I submit a form on a website is a good way to make me log out and look for alternatives to whatever service I'm using.

To me, the question is this: would you rather give 100% of your users a kinda shitty experience, or 99% of your users a normal experience and 1% a nightmarish awful shitty experience. The answer probably depends on use case.