Is artysta a masc. noun? Looks like it should be feminine by default
Yes, it's among those masculine nouns that look feminine. The feminine equivalent is "artystka".
What does artysta actually mean? Is it someone who's involved in some sort of creative creation? (I mean, artist doesn't usually mean writer in English, afaik.)
The same as in English. I'd rather associate it with paintings and some other visual arts, but it's just someone who creates works of art.
Shouldn't it accept a female artist too?
Of course it should. Added "Ta artystka".