I would say your score just barely passes as good or "ok"
this is how I judge myself in every game i played in terms of if i fed or not
0 deaths = perfect game
1-2 deaths = Good game
3-4 deaths = allright game
5-6 deaths = I could of done better :/
7+ = omg maxwell you fucking feeder
But then we have the LOL kda score
KDA is Kills+Assists/deaths
KDA of 2 or lower = bad game
KDA of 3 = decent game
KDA of 4 = good game
KDA of 5 or higher = Maxwell you were a God
your kda
4 + 21 / 6 = 4.1
So with my deaths grade and the LOL KDA grade I would say you had a decent game, you did pretty good. If you are the type of player who constantly reviews over how you do like I am, then use these two grading charts, it's a great way to start off your analysis before you get into deeper detail such as the plays you made