@Riot why is Teemo's range so pathetically low and why is Teemo an assassin?

I have noticed when i play Teemo support for fun in normals that literally almost every ranged champ in the game outranges me. His Q range is also lower than most AA ranges and don't even compare it to most abilities in the game. Each time Teemo wants to trade he loses the trade because a) his blind works awkward, b) before he can click Q he has already taken damage from longer range AA and then the enemy retreats, c) His AA range is so low he gets poked down, cc'ed, nuked etc by every ability in the game.

Assassin style: So the only way to play Teemo is to plant a lot of shrooms and camp somewhere stealthed hoping a) the enemy walks over shroom and b) he doesn't have red trinket (which they always get) clearing all your shrooms and exposing your position and sometimes even c) he doesn't have QSS countering your shroom and blind and thus leaving you unarmed. And due to red trinket and the fact you get bursted very easily it isn't a rewarding playstyle. It is also a toxic playstyle. There are better champs who can get more reward with less risk involved being played as assassin.

So I don't see Teemo as an assassin. He is a scout and he is not fulfilling this unique role as much as I would like him too. His map presence is sometimes nullified too much.

TL;DR: Why do champs like and have higher AA range than Teemo? And why does Teemo has such a low AA range compared to every adc in the game?