I think my previous post got shit-canned because I had a too-confrontational tone, but I think the points are still relevant, so let me try again.
>email verification, 10 minute cooldowns
A slight correction: It's 15 minutes, and that's the initial "join" cooldown. It also gets skipped by E-Mail verification, which is totally optional for every board except /biz/.
(Unless you're referring to starting new threads, which I'm pretty sure took only 5 minutes.)
>captcha
I still haven't gotten this complaint after reflecting on it for half a decade. Moot implemented a far worse version of the captcha in years past, and all Hiroyuki's done is tacked on additional difficulty levels, hCaptcha and reCaptcha for initial verification. I'd hardly consider that "killing itself."
All of this was done to at least temporarily curb AI traffic, and a question of how much of 4chan's traffic was chatbots.