Ezreal is not easy champion.
He has a flash but so does many other adcs while having 0 mechanics other than right clicking.
Ez requires spell weaving to do any meaningful damage, his skillshots can be body blocked and hes like no damage to tanks.
He has to hit a W Q on someone squishy to even do 1/4th their hp and even then they can just lifesteal, missing 1 skillshot in a duel is pretty much a loss for you.
Ez can be safe and just stand back and press Q and E the moment someone gets near by then he just becomes a chase bait while your team kills the enemy, and god forbid if they have a hyper carry adc who can shread everyone. the games i win the most as ez is when i can pick the enemy adc/mid laner with my burst before a team fight.
Ez is very weak to ambushes and sticky champs, even with a flash if the enemy has a eve/rengar who is actually decent they will 1 shot you before you can even hit the E key, samething with shit like jax who can still catch you with his super low CD leap strike and using his counter strike to dodge Q's.
I play a lot of ezreal and there is very rare a time i will hard carry a game unless i get super fed by being ignored mid can push all turret plating and run into 18 mins with gauntlet/fully stacked muramana. most time i get camped pressured and dived.
Ez has a high pick rate, because he is one of the few champions that are very very fun and his play style can change from ADC to Mage, very few items are a bad buy on him an he can adjust to be whatever he wants without giving up to much damage for it. he has a versatile build path and isnt just the same old ie rush into zeal item adc.