The demo account is just for educational purposes and doesn’t guarantee success alone. There is emotional balance which is very important for traders to make winning trades which the demo fails to inculcate in them.
Both trading accounts require different approaches to trading. That doesn’t mean demo accounts are not useful (because you can’t take risks on them). In terms of skill development, demo accounts work the best. Use them to sharpen your trading skills. Later, you can switch to a live trading account.
Forex demo accounts do not ensure success while trading live. It is only apt for educational purposes. But that does not mean one should ignore the demo.