It's not that they can't trade anymore. From what you've described, I believe these people are overly reliant on AI results in their trading. Reliance on AI tools can make traders feel less confident in their own abilities, It's best not to overly rely on AI results or apply them to your trading. AI, as we know, can provide analysis and predictions, but it's important not to rely entirely on it. Developing your trading skills independently and experiencing firsthand each indicator you use while trading is far better. This will give you confidence and the ability to make better decisions based on your understanding or analysis.
If somehow they were better than humans, then yeah it would make sense, but that doesn't mean we are going to get great results, it just means we are going to get results that we want, or prefer. This is why it would make more sense to just focus on our personal way.
Because if you do it yourself then nothing can take that away from you and that has to be the most important part. If you can do it yourself then you will be able to improve and do a good job and unless you get some brain injury then it will always be with you

But if you use AI then it's all technical, even a new update could break it and make you lose, so there is really nothing that you control, it's all outside of your control and you can't do that great.