Teemo needs a full rework for his gameplay. He's way too toxic and It's pretty outdated. It has absolutely no resemblance of a scout aside from maybe his passive, but I think a scout should be more than just AFK'ing in a brush until some idiot forgot to buy a sweeping lens, and then just spamming auto attacks on them until they die.
The thing is that Teemo has such a huge fan base that Riot probably couldn't touch him like Lee Sin. Despite Lee Sin being overpowered by all means, and I'll willingly spend hours discussing it with someone, Riot can't really nerf or rework Lee Sin without his enormous fan base going insane. This includes other broken, gimped, outdated or just outright toxic champions who have a gigantic fan base. I believe Stonewall mentioned some others being Irelia and Shaco but I know for a fact he brought up Teemo needing a rework, but simply due to his fan base he won't ever be reworked.
I agree that there are other champions that need some love, rather than Teemo, I'd prefer him to stay in his more-so underpowered state rather than an overpowered state which would be an absolute nightmare. I think the champion overall is underrated and he can actually do more than just sit there and do damage, but people in higher elo will just abuse him as free kills whenever possible since after early game, most champions outscale him and he also can be really reliant on his mushrooms which can be totally avoided, It's annoying and tedious but it can happen.