Ezreal is not weak, he is actually always a mediocore pick or better. I can't recall a single time in history where he was a bad pick. He is always at WORSE mediocore. All though it is true that he has a low public win rate right now, but stats aren't everything.
Ezreal has lots of safety in lane because of his E and Q, he is able to farm from a long safe range, and the moment he is in danger he can Blink away, not dash, but blink. Most jungler won't even bother to gank a lane that looks like this.
Like how the fuck do you gank that? Answer, unless Ezreal wastes his E, while you the jungler so happened to be strolling by. You can't, you really can't unless they are over extended up the ass.
But that's just the defensive side about Ezreal, what about his damage?
Early lane phase, a good ezreal can be very annoying to deal with, for since his W is not blocked by minions, assuming you have "Skill" he he xd you will be constantly landing efficent poke while farming minions. The moment your support lands CC, even more easy poke. Eventually your opponents will find themselves at that risky 50 40 percent health range while you are just annoying as fuck blonde kid with 80 percent health spamming "you belong in a museum"
Itemization
Ezreal is a nice champion for he is one of those champions who can honestly build whatever the fuck he wants, and it will some how make sense. That means, unlike other adcs like
who has no choice but to go a strict crit build or
WHO DESPERATELY needs attack speed. Ezreal can adjust his build completely dependant on who he is facing and it will be fine. This is largely because of his Q and his passive. His Q is on a reletavily very short cooldown and basically becomes his auto attack. Meanwhile his passive is buffing his attack speed, so you don't need to worry about rushing attack speed on Ezreal. I mean sure it helps, but it's not the end of the world if you rush other items first.
Team Fighting
Team fighting is where Good ezreals become hell. Through E they are able to relocate wherever they wish and use it however they wish. Wise E useage will make the enemy team feel like they are fighting a dragon ball z character and they will hate it. Through Q and W Ezreal is raining consistant DPS upon the enemy, and if some stragglers feel like running away he has his ultimate to chop them down, which scales very strongly into the late game. Plus with the fact his Q can proc things like Iceborn Gaunlet, he can become a slowing AOE bot. Late game where his tear is fully stacked and he gets the damage passive along with his bork, Ezreal will just shred enemies a new one. Peel for him and he will carry you. Ezreal imo is one of the last remaining Solo carry adcs, where if you know him to perfection, he will legit 1 v 9.