The mathematicians who complain now had no worries about the way the generous idea of open access turned into the gold open access, where the author pays for publication.
These people have no problems with the phd students who are forced to publish or perish and even if they survive there is no future for them.
Now the problem is IMO that for the first time the interest of the publishers and academics are not aligned.
Publishers want more articles to sell back to the academics.
Academics are pushed by the system to publish more.
But all the work is done by academics who write and review the articles.
And also a huge inflation of articles devalue the publication unit.
So a CAPTCHA idea is only natural, even if the kind of a malefic idea a manager could have.