Trading is more a game of skill than just luck if you like to describe it in the sense of a game. People who master this skill become better over time; their win rates improve with consistency and practice.
If you think of trading as a game of luck, you would never really put in the effort to develop the skill required to be successful in that field.
It is more than a game of skills but it is a game of skills and traits. Your personal traits decide what you do, how you do it and even you learned well about trading, knew of good skills for trading but in your trading practice, you can fail by your bad personal traits. For example, if you understand trading well and apply a good trading strategy but if you lack of discipline, patience for your trading actions, you will fail and lose money in trading.
It is not because you are unknowledgeable but you don't have necessary personal traits for trading success.