Divers, Skirmishers and Assassins are often described as unfun to play against

Try to figure out why they're described as unfun to play against and figure something out from it: Divers translate initiation power into threatening the hell out of somebody(s). Skirmishers are designed around the ability to take down opponents in 1v1s. Assassins are picked for the sole purpose of ruining the carry(s) day.

See, a common element of these roles is that they are designed around beating someone into the ground.

"Oh okay, let's balance them around not beating people into the ground"

Well then you don't have Divers, just inefficient Vanguards that neither bring the CC nor punch to be worth picking You don't have Skirmishers, just little meatshields that dance everywhere (or worse, Tank Ekko) You don't have Assassins, you get teleporting meatshields, or annoying champs abusing weird utilities like Zed in his prime

In my opinion, the fault doesn't lie in Divers or Skirmishers or Assassins, or Battle Mages or Juggernauts or anybody else that's balanced around their combat prowess, the fault lies in spoon fed crybaby players that have convinced themselves that a grey screen means its the game's fault and not theirs.

Diver, but more so Assassins are going to be focused on catching the squishies out. So the counterplay to that is not get caught out. That would require them to help secure vision, (not just rely on the support) and respect the lack of vision. Yet in Lower ELO, that never seems to get through their thick skull.

The other issue is just peel. Almost no one can duel a good skirmisher, a most ADCs don't have self peel.

Really the people who find these guys frustrating, are the glass cannons, who really do need to rely on their teammates. (Like they always have.)