Trading is really a mental game more then indicators and fundamentals. The whole system works on how do you think when you are in trade.
Is trading simple? - sure seems easy enough - just hit the buy or sell button, not exactly rocket science. Trading is so simple we have had some ET's trading from their cells while driving for Uber & Door Dash.
OP seems to be both asking a question and making a statement. Next time he starts a topic, for clarity sake, I suggest do one or the other.
Like with exotic options; the payoff are easy to comprehend but difficult to model. You can only buy and sell yet inherently difficult. Actual trading (not passive beta) is hard. Either you have a small edge and high hit rate or a large edge and sample size is limited (were you simply lucky?).
What makes trading complex is that there are so many unknown variables, some variables that have not been accounted for, or some interrelationship that we did not see, etc. The variables are not just in the market, but more importantly in the traders’ psychology. First of all, you need to understand that when you’re developing edge, you’re basically back-testing arbitrary patterns around concepts with the intention to create some kind of order, which usually only works until the market conditions change. Therefore, it’s better to forget about any indicators, and instead learn how the markets actually work, how to frame the market with just price bars and volume (and nothing else), how to identify buying and selling pressure, and then start developing your edges based on that. That way your TA edge will remain regardless the market conditions (eg. up, down, sideways, quiet and volatile conditions). Anything simpler than this is asking for problems. After you have developed robust edge based on trade logic, then you meet your profit objectives and risk appetite through position sizing (which is a part of risk management). Initially the above sounds complex, and it is when you’re developing as a trader, but eventually it becomes simpler and simpler, and almost subconscious. However, to trade well, you must have your personal psychology together, otherwise self-sabotage (fear, greed, need for excitement, etc) kicks in, and then discipline and executing according the plan can be problematic.