Demo trading is like trying the platform itself, familiarizing about it though you can do the actual trading but there’s no risk on that and your emotion might not be present by that time but still using a demo trading at first is a big help.
I don't think demo trading has actually helped anybody learn to trade.
A couple of years back I tried forex trading with a demo account and it felt like I was learning because I was making profits, but when I started trading live, I lost all my money. I think that's part of the reason that discouraged me from foreign exchange.
What I find most annoying about demo trading is how easy it is to trade and make a profit. All this is to make sure you trade on that platform.