The less they train, the longer it takes. "for fun" is a vague term so hard to say if that would entail taking it seriously enough.
The definition of "artist" is - person skilled in a particular task or occupation.
So "skill" plays a part but (imho) so does passion, commitment, desire. Without these things, NO, a person is not a martial artist. They're just a hobbyist or (more appropriately) a tourist.
Hey, I get it. This is a feel good place where everybody wins just for showing up. A guy can strike out every time he swings a bat and not care enough to practice before his next game, but it's ok, he's a "baseball player".
Now, on the other hand, if that same guy is doing "axe chops" in the gym, working on accuracy drills, studying the mechanics of the game, and the first thing he thinks about when he wakes up is how to get better BUT he still strikes out. Yea, that guy is a baseballer, crappy one who loses a lot, but wtvr! He's willing to invest chunks of his soul into something he loves. THAT is art.