A KDA of 2 is average, a KDA of 3 is good, a KDA of 5+ is bad
If your KDA is 2 you're average.
If your KDA is 3-4 you should be climbing, but if you're not it might be because you get troll teams and AFKs or just unskilled players.
Seriously, if your average KDA of over 5 over a large sample of games and you're still in the elo you're in without climbing, there's something lacking in your game sense. Your mechanics are definitely there, the next question is, why are you not climbing. At that point you can learn the answer to that question and fix whatever it is because it's your lack of game knowledge and not your teams holding you back.
And if you are climbing, eventually you'll reach an elo where you will no longer be able to pull off 5+ KDAs every game, so your average KDA will drop to a reasonable number.
. I didn't play a lot of brand prior trying him out. I don't particularly like trying new champions on my main in normals just because I will queue against players that are still close or around my mmr and it inhibits my learning. The account was silver V and now its Gold V.