He is not exactly trash tier,he is situational(too situational imo),an adcs job generally is to output a lot of dps,which ezreal doesn't do very well,there are also better lane bullys out there,so if you are looking to win(ezreal is good at not losing lane) lane there are better picks.
I sometimes see him do well(i mean as a pick,i quite often see ezreal simply do well,but can't help but feel a mainstream adc would do even better),but it's a rarity,you generally want a team comp focused on poke+siege+disengage+kite which don't happen often,generally aren't very solo q fitting(mostly because people just pick whatever they want(not saying they shouldn't,this is simply the way it's generally is),which just doesn't end up in this sort of comp),and even if you do manage to get into such a comp,all it takes is one guy to go rambo as he isn't used to playing in such a way to mess it up.
Overall i think he may(not entirely sure about where the latest changes put him) need some buffs,so that he may be an actual situational pick,instead of something which theoretically can be good,but practically you just never get the comp to make him fit.