How much work is making a Minecraft server from scratch? What things need to be implemented? I saw on the GitHub that placing and destroying blocks was implemented, so I’m guessing it’s a lot of work

Depends on how simple you mean. I’ve made countless games that are super simple and took just a couple of hours. I advise that OP makes one of these games and not a “real” game since I honestly don’t think ChatGPT can make a big game without a programmer that knows what they’re doing