I understand Ekko's high damage, but people should understand that this damage is quite slow and takes quite alot of time.
In terms of his CD, 9s is not low. If you catch him in CC, he's dead unless you don't have the burst. He is horrid against people like Zed or Diana or Talon, or any mages that can snare and straight up one shot burst his entire being. If you are playing someone like Brand expecting to kill him 1v1, then of course he gets the opportunity to escape.
Also, his aggression early is not safe at all. If you take TP and push the wave (which you should), I can say his aggression levels 1 and 2 are safe, because he can just go back, get some more mana, and be ok until he needs to back again. However, in both cases (whether he takes ignite or tp) if he focuses ONLY on the wave, he cannot really spend time trading. Using Q so much takes alot of mana, and if he uses his E and W in a trade that he did not start, he is already in a bind. I already said this before, but people who out sustain him or can harass him heavily (Vlad, Ori, Cass, etc.) make his laning a bit more complicated than simply pressing Q to win like how most people here think.
His laning isn't safe at all unless he stands under tower and Qs, and Ekko only does that with this bad matchups. You'll never see an Ekko try to trade w/ Azir ever. That's just him playing the mid game.