Why nobody picks KOTL anymore?

Well, KOTL used to be high picked, but now it's rare to see a KOTL playing...

He was not nerfed in the 6.9, so, what happened?

He has no disables, he dies really quickly and there are supports that are way better than him.

Well, PL and him are the duo who only get picked when they are together, but that is to obvious if you pick up 1 than the enemy bans/picks the second one :p or picks gyro/kunkka xD
But I do not understand why he is not picked, he could have a lot of sinergy with something like a sky, but than they lack stins for instance.

Heroes rotate out based on how the meta shifts, Keeper of the Light was a strong pick because at the time other supports were weaker in serving the role he was picked for which was mostly lane dominance and pushing / turtling. He fell out of the meta when Phantom Lancer left the meta for a reason. Now we see Crystal Maiden for mana, but the reason she's picked is because she is an excellent roamer and Venomancer is picked for lane dominance because he can push the opposing laner out with relative and reliable (Illuminate is unreliable) ease. The lack of an sort of CC and his only reliable disruption being Blinding Light (disruption being very important in cancelling TPs, which everyone in high tier will have on them), on top of the shift in less right-click carries (Evasion on Blinding), and Recall not being needed for base pushes (Because Nature's Prophet is the current high tier back-door hero, which was formerly Anti-Mage). I find Keeper of the Light pretty high up there in liability if your early game fails (much like Chen).

I am going to have to do a lot of disagreeing and agreeing as I find KotL quiet fun to play as (currently still practicing against bots)and I discovered when playing with a friend that KotL can be really helpful to DK early game as KotL can harass the other heroes which leaves DK to farm. KotL can also give mana to DK which he in turn can use his nuke quite consistently thus enabling him to farm, stun and possibly get more early game kills and also push the enemy tower more. I also find that his mana drain can be useful when an enemy is running away from a group, u can use it and hope that they run of mana to try and cast a stun or TP scroll, however everyone can just stand still to counteract it.
It is true he has unreliable abilities but if he is used correctly under the right circumstances I believe that he is just as effective. More so his blinding light is useful in the early-mid game team fights.

KOTL is squishy and he cannot support another hero by himself since he himself needs setup for the Illuminate. KOTL doesn't have a good disable and if KOTL is caught off guard, he's dead and since defensive trilanes got hit hard in patch 6.79 he fell out of favor. The point of picking KOTL is for the great defense from Illuminate, Blinding Light and Recall so if that's not needed then there's no point in picking him.

MID game comes around much faster too and KOTL's mid game is terrible. Thanks to the nature of KOTL's skillset, he actually need levels compared to other support like Crystal Maiden and Venomancer. A level 3 CM/Veno is far more useful than a level 5 KOTL under similar circumstances and KOTL doesn't have the CC nor damage other supports have so that's even more of a reason not to pick him.

KOTL cannot roam or gank other lanes to help since he has no lockdown and Mana Leak is rarely picked up early since it'll just leave Illuminate and Chakra ranked 1 at level 3. Going 1-1-1 at level 3 for KOTL is INCREDIBLY ******ed unless you have adequate setup.