I have been trading for so many years and yet to be perfect in my trading.
Honestly, I can see lots of improvements in my skill in theses past years.
I make some bad trades a few times, but I am still very much profitable compare to not knowing how to trade at all.
In my opinion, the market is very broad, dynamic and involves emotions, hence the reason it takes so much time to master.
Knowledge is a never-ending path; no matter how far you feel you've gone, there will always be more to explore, which means that no matter how much knowledge you gain in the world, you will still not know everything out there; that's how broad it is. When it comes to trading, spending years should make you a decent trader, considering you have been trading throughout this time which means you've gained experience as well, and if you think after so many years, you are still not a very good trader, it means you are still not doing things in the right way.
When you feel that things are still not working very well for you even after spending so much time and money, you need re-evaluate the process you are using, and also double-check the knowledge you've gained only to see if you have the up-to-date information about things, and that you are using the right practices for the right situations and conditions.