When trading using real money, thinking will become even more sensitive because thinking will become more tense when real money is played in trading, plus they will be required to win if they are not profitable then psychology will be disrupted and that usually happens to those who are beginners who are just trying, and indeed a demo account as a lesson but will not provide any experience if you don't use real money.
Starting with theory and then practice, it will indeed be better. Real trading experience will provide a lot of experience, especially how to determine the strategy if, in an emergency, psychology will be played.
When not profitable and lead to losses it will be a lesson that needs to be corrected first.
Psychology will be stronger if we face all markets and not just wait for a bullish market.
I never do demo trading, I just start with theory and then apply it to real trading with a little money that is only used to learn.