If you're struggling with bot activity, there's lots of different solutions all with varying levels of reliability, you could go for extreme solutions like text message verification, or email, or you could opt for ReCAPTCHA, which seems to be the hardest to automatically complete, though it's still possible, but the pricing for recaptcha completion is the most expensive lol. You could opt for creative solutions, like something I see Linux wikis do for verification is "what is the output of <bash command that is likely somewhat computationally expensive even if nominally>", but most captchas are easy for bots to do, but hard for humans to do, or so annoying that nobody is going to bother.