I have tried it, I had a business idea from many many years ago, like maybe 10+ years ago, and I asked chatgpt to write me a business plan. It doesn't do anything that you can't do, it just gives you the main points that everyone who has even checked any business plan would know, it's good to have for detailing them, but it's still that you need to find.
Plus, if you want to have a good business, you need to end up having some funds, and chatgpt can't help you with that. Majority of the big companies in the world did not start with zero dollars, they started with some funds, either from the creator, or from investors, that's how you become bigger.
Amazon took longer than a whole decade to make some money, they literally write off debt and loss like it was nothing, and they kept on growing that way, now they can make billions easily thanks to that. This is why I highly suggest that you do not trust some AI to help you build a business, while it can help you a bit, it is not going to be your assistant that tracks everything down, plus after writing for a while, it gets clogged down and you have to restart a chat, you can't just chat on the same place for many years, hence why it will fail eventually.
AI may give you good business plan but the implementation is another story. That is true, AI can give you walls of texts but that's it. How can you start a business even a small one if you have no funds to begin with? Aside from that, do you have the knowledge and passion for the particular business you want to explore with?
Also, you need to check if that business plan is applicable in your current environment. Some pointers may not be suitable in your situation, hence, you need to modify those plans according to what is in front of you.