i dont really think he's overpowered.
He's just reliable. In the sense that he is one of the only junglers who are mechanical and mobile enough to not require laners to setup ganks, and is easily able to counter jungle. Most junglers are dependent on laners having priority or just outright winning their lane, whereas Lee and Elise are able to take the reigns of their own jungle experience.
However they arent as strong as other junglers are when those junglers are on teams that have players who understand how to set up ganks, understand jungle routes, and understand lane control.
BUT as we all know, most laners just play on autopilot. Theyre good at micromanaging their champion but they have little understanding of macroplay and virtually zero understanding of jungle macroplay, so they generally arent going to be setting their jungler up to succeed, but rather to fail.
Which is why Lee and Elise are such prominent picks, because junglers CANT reliably depend on their laners to understand the game outside of their 1v1/2v2 microplay lane expereince.