Wasn't captcha designed precisely for this use case?
Nostr is superior, it's much more agile and versatile, thanks to the LN integration.
X looks more and more like grand'pa technology.
Discussion
Yes, I don't get it. The current sign up uses an even more complex proof of work/proof of human tool than a capatcha, you have to solve several differnt puzzles in a row. How that doesn't defeat the bots begs the question, why have it at all?
Possible that bot operators hire slaves in 3rd world countries to open accounts... 🤷♂️