What is the strategic point of picking Teemo?
Like, as far as this game goes, why is he here and what useful niche does he accomplish?
Like, as far as this game goes, why is he here and what useful niche does he accomplish?
He's a heavy melee counter champion who split pushes ... decently.
He also offers good objective control (around Rift herald and Baron specifically).
He is also a counter to many ADCs in teamfights with his blind.
His blind allows him to nullify AA hits. It's good for killing any AA reliant champ
So his primary niche should be "Countering marksmen"?
So, for instance, if his kit were better designed, that's what his main thing should be?
He has several uses
Let's not bs an answer. Real in-game niches. You know, you don't say "I use White Mages to distract people from my Black Mages". White Mages are used for healing. With this in mind, what's Teemo's in-game role?
You think i'm joking, but I'm not. Any Teemo player will tell you that he ends up drawing attention. That is a great reason to use him because it takes attention off of your other carries. As for teamfights, his Blind-Dart helps protect your team from high AA damage dealers (non-caster focused ADCs like Jinx Ashe and Cait), and every Teemo builds Frozen Mallet giving him high kiting ability. His Ult Shrooms are used for area control, sure red trinket can disable them but then the enemy team has to choose between sweeping for Wards or sweeping for Teemo Shrooms helping your team's vision game. Finally, Teemo loves to flank squishy champions. He's one of the champions that can do it better than any other. If you're playing Teemo standing next to your teammates instead of getting behind the enemy, you're playing him 100% wrong.
teemo has many effects in game
Psychological effects like where is he ? where are his shrooms?
he is good at hit and run. splits pretty safely more so if he gets ahead
and the biggest factor his his map control and vision. sure there is his blind as well
but you give a teemo 5 mins to set up baron/dragon and its free. period. the map becomes a literal mine field that causes the whole enemy team to upgrade sweepers to stop and take down every single one or take 50% hp or more damage from stepping on one
teemo is easy to learn and hard to master but once you do master him, you will enjoy being called a evil little bastard... I assume...
He used to be great at map control, he could hold a large majority of the map for his team with well placed Mushrooms and keep enemies from having as much vision due to them having to buy 
Now though thanks to all of the anti trap shit Riot has added in addition gutting his Shrooms for a fucking toss gimmick, he's just another early game cheese Champ now where you hope and pray that your enemy is dumb enough to let you spiral out of control top-lane so you can splitpush and hold the enemy team's attention long enough for your team to get a lead.
There is literally no point to picking Teemo other than personal preference and I fucking hate that they did that to him. You can't even say that he can counter marksman because his Blind has a travel time that can let 2 600-1000 Damage auto-attacks through effectively making it a 50/50 "I catch you off guard and blind you or you 1-shot me before my Q registers on you."
i pick him when i'm in a good mood to spam laugh and flash mastery, never ranked, ever
His role in game is simple: a tumor. He's deadweight and he's going to get a bunch of champions and minions killed. just pray to god it's the enemies who drop dead from the pick first.
Tilting other players.
Both on your team and the enemy team.