Professionals watch what is being traded (as it trades) and retail doesn't even know what's being traded. They don't know what is driving price, in something like ES.
That's why they are always talking about retail techniques instead of the trading being done by the institutions and the techniques they use - things that actually affect the market.
Obviously, the institutions are doing the real size, and retail is not. It follows that you should be watching them and learning about what they do, and how they do it.
This last part is a closely guarded secret in the industry - proprietary information, trade secrets. They make all their traders, quants, and support people sign NDA's and non-compete, etc.
The most important thing in the market is rate differentials and basis spreads - index basis and treasury basis. Real edge is based on reality. It's naive to think that retail is getting ahead of anybody by using backtested entry strategies, simplified technicals, or market depth/order flow.