Counterplay doesn't just mean whether or not they can hit you. Builds, strategies, and plenty of other elements are also counterplay. Building Thornmail against Fiora is huge counterplay.
As for strictly numbers, Ekko really isn't that much stronger than other champions, if at all. ALL of his abilities can be either dodged or easily dealt with. Every one of them.
His Q takes a full two seconds to return to Ekko. Two whole seconds. Walk away. It doesn't do hardly any damage unless both halves proc.
His W has a 3 second delay. "But hold on Lao Fu! Enemies can only see it for half a second! So it's really only like a 0.5 second delay!" Wrong. It still has a 3 second cast time from Ekko's perspective. PLUS, you can SEE and HEAR when he says "Step right up!" which tells you flat out, "Hey, I'm casting a stun zone, so you better move."
His E puts him in melee range, and for some champions who love close fights, like Annie, Swain, and Diana, this is great.
His R he LITERALLY CANNOT AIM. He cannot use it to damage you unless you foolishly walk on top of it (or if he's in brush). 85% of the time he's using his R as an escape tool, not an engage tool. He only ever has a chance to use it as an engage if you are chasing him. Plus, if he doesn't hit R immediately when he realises he's in danger, it'll just place him close to the fight and he could still die.
People can ask for hard nerfs all day and circlejerk their way to the top of boards, but the fact of the matter is that while he's good, he's not OP or broken or whatever word you want to use. He's good. He is, in my opinion, in a decent place, and I've never once felt like he was "too strong." If he beat me, it was because he played better than me, and that's it.