Why is talon played so much on the top lane? when people say he's bad on that role?

Cause he shits on melees in lane IIRC.

Eventually your team is left without a strong tank though if your JG and support don't pick tanks.

He has an easier time on melee champions because of his passive and enhanced melee range Q damage.

only cause he gets shat on by every mid lane ranged mage. eat poke even for trying to hit any minion

You can trigger passive multiple times, forcing the enemy out of lane. Has much higher winrate then mid

I don't think he's bad top, more that he's bad for his team top.

Talon's passive helps him get a ton of early game kills, which gives him early game damage which he can then use in other lanes. If he's mid lane, he can roam either top or bot and help them. If he's top, he can only sorta roam mid. If he does roam bot, he's going to miss a ton of minions top unless he communicates with his teammates and gets the mid laner or jungle to roam top and hold his wave. That's a lot more coordination needed vs a mid Talon who just roams bot and uses the terrain to get back to lane with minimal minion losses.

Additionally, normally mid lane is squishy, so unless your jungle and support are tanky, you're denying your team a tanky member by running him top. So Talon absolutely needs to snowball if he's top cause otherwise his team not only loses a laner but loses a tanky or CC champ. If mid takes Galio or something, that might make up for Talon being top, but it's unlikely in solo Q that teammates will try to make up for another champs weaknesses.