You did not add the aspect of how to actually trade and everything you explained are basic things everyone will do to be able to trade. The most important thing being to choose a trading strategy which they must test in demo and confirm the performance before they can implement in a real account. This is where most traders fail, they start trading without a strategy that have been tested and verified. If you try trading without a strategy, you will learn the hard way.
Yes you are right, what everyone needs to learn to trade is the rules of training, fundamental analysis and experience. Without these, trading is almost impossible. But if you are new, you can gain some skills and knowledge by using a demo account. The main reason why beginners fail is that they do not test their skills with a demo account and start trading in the real market. I would say that until you learn proper trading, you can test how much skill you have gained with a demo account. Yes, you will fail only when you trade without a strategy, so I would say that you should gain the skills of trading and profit by trading.
Trading using a demo account is highly recommended for beginners to understand the basics of trading or as a field of practice for implementing the theories and strategies you have created for your trading plan.
However, I myself did not use a demo account when I first started trading. To be honest, I experienced what you described and jumped right in without any specific training or testing, which meant it took me a long time to start making a profit from trading. I admit that was a mistake because I was careless, and it cost me a lot to pay for that carelessness.
However, what is certain is that everyone must go through their own phase to find their path. Sometimes other people's strategies do not suit our own trading strategies. I once tried using someone else's strategy, and it proved successful for them, but when I applied it, it did not suit me in terms of emotional management and trading targets.
In this case, it is better to use a small amount of money to test your trading strategy so that you do not incur significant losses if you do not want to use a demo account.
The key is to keep moving forward consistently in your learning journey. Never be arrogant in your learning process. Results will come to those who are consistent, even if it takes 5 to 10 years and requires many sacrifices to understand the right trading approach for yourself.
Still believe that effort must have results.

Trading on a demo account really gives beginners a safe space to learn the basics test strategies and understand how the market moves without risking money but many people including myself started without that step and the truth is it makes the learning curve much more painful jumping straight into real trades without testing first often means paying for mistakes with real losses and it takes longer to reach consistent profits.
Every trader eventually realizes that not every strategy works for everyone emotional management risk appetite and personal goals all shape whether a system will suit you i’ve seen strategies that worked perfectly for others fall apart when i tried them because they didn’t fit my mindset or my style of handling pressure that’s why adapting and testing for yourself is so important.
If someone doesn’t want to use a demo account the better option is to start with very small capital think of it as paying tuition for real market education that way the lessons don’t cost too much but you still feel the emotions of trading which a demo account can’t fully replicate.In the end progress comes from consistency patience and humility it’s not about rushing results or being arrogant thinking you’ve mastered everything too quickly trading can take years even a decade before real stability shows but steady effort always leaves results the important thing is to keep moving forward and not give up because every mistake and every sacrifice builds the understanding needed to finally find your own approach.