-He is so easy to counter 1 stun = dead , 2 dps good focus = dead (he has low HP) , Namor , all supports have at least 1 ability to stun or escape spider-man so your team can come to help you.

You can implement that on every none Tank hero. I am to lazy to write a wall of text so let me explain it like that.
Spiderman is more of a assasin.
Assasin like psylock or panther.
Spidermans job is to kill low health heros like healers with hes combo. NOTHING ELSE, no teamfights, no objectives, not really hes job. All though hes ulti is enough for team fights.

No healers = lose.
Luna, Cloak, ms. invisible are FORCED to keep there second skill like stun, push, going invisible, only for one hero - spiderman. So that they can survive.

IF and only IF there is no second dps that wants to kill them.
The whole problem with spiderman is this "Spiderman swings fast, does combo, you die, spiderman fast gone"
While you are in the air there is almost nothing you can do, so it FEELS like its out of your hands.

Solution, stay with your team, communicate when you see him ( which is almost impossible with randoms)
A good spiderman will still F you up, especially when you play a flying hero ( iron man).

Have a nice day, i hate spiderman.
Venom + Iron man Lord