Swain is a "ball of stats" champion that should never be allowed to be strong.
What does being a "ball of stats" champion imply? It implies the champion doesn't require skill to play, they just need to have more stats than whoever they are against and then they point and click and win. Swain fits this idea completely. His stats outscale whoever he is laning against very quickly. So quickly that if he doesn't die before his first recall that is enough to outscale almost anyone he lanes against. He can return to lane and immediately jump on them and right click and they will die.
He's too strong for how simple his kit is. He's the epitome of click on enemy to dive and and win as long as your stats are superior no outplaying required.
When laning against Swain, the burden of outplaying is always on his opponent, not on him. He "outplays" his opponent by not dying and waiting until the moment he has better stats and outscales whoever he's against which usually happens by the 1st or 2nd recall. Since Swain's opponent has to harass and kill him early on to win he has to push the wave and show aggression which leaves him open to being ganked. If you die to Swain a single time he's automatically ahead and you are no longer allowed to CS. If Swain dies to you it just takes a little longer for him to reach her outscaling point.
He doesn't have to earn his power it just happens from not dying early it's too easy for how strong he is.
He needs nerfs until he is reworked. He should be bottom tier like cassieopeia until the rework arrives.

exists). He is too strong right now for sure and does have some problems with his kit that could be better, but he isn't what you are calling him.