Captcha?

So as ya'll know, we've got a ton of bots everywhere, and since some of them are pretty terrible, especially for a kid friendly site, I was wondering what it would take to put a CAPTCHA in. I'm not sure about the logistics of this(or even if this has been talked about) but I think this would be useful to stop bots, since it's a prevalent problem on here. If it's possible, i think it would be gr8 to put one in. But since there isn't one, I'm assuming there's a problem, either with the costs(especially since covid) or how the website works, so I was wondering why, and how we could circumvent that.
Unfortunately there already is a captcha on sign up. The bots or whatever this is, are smarter than that. There was an issue with v1.8.27 of MyBB that allowed bypasses but given this issue of spam accounts predates that bug being introduced, I am not sure that they are just bypassing.