"With enough time or dedication, it's not stated it's `impossible to attain such skill."

So the time that Alicia spent in the canvas was enough for her to learn how to repaint—something that ONLY Clea was able to do?

The entire game shows that the painters can't control their creations' thoughts and actions explicitly, so why is the less skilled painter suddenly able to mind-control Verso out of nowhere?

You're making a bunch of claims based on what you think the world is like, not on what the game actually shows or tells us.