It would take time to learn skills and tricks in trading. Let us put it this way, it is not an overnight task to begin with. Every trade is unique, and from there, you will gain new insights that can equip you to execute the next trade.
Strategy can indeed be learned in a short time. But in its application, we will need time to finally be comfortable enough to trade. Trading cannot be learned overnight. There are several factors where the experience of trading that we have done ultimately becomes the most important in our next trading activities.
You are right; trading is unique. We can follow the procedures that we may have learned well. But the market situation forces us to adapt to some developments made by the traders themselves.
Talking about theory, we can learn it in a very short time, but as you said, the implementation is what is difficult. We will find many differences and sometimes we think that there is nothing in theory at all. In addition, the mentality will also be very different.
When learning theory, we will not need a mentality, because we only read books or we only listen to mentors (if we have a mentor). However, when we jump directly into the market, our mentality will work because we bring real money to trade, which can be lost and can be profitable.
In my opinion, mentality is more difficult, because it will work within us and it will also affect emotions, while in trading we must be able to maintain our emotions.