Good players can play any character, even bad champs, and still do well if not astounding against weak players. That is a testament to the player skill and not the champ. Speaking objnectively as possible about each champ though is different. Ezreal is just a really bad champ and has been for a long time. I think they gave up on fixing him though since they haven't touched him since they nerfed him hard to the point where people only play him during a free week.
There are several chars that do good as hybrids but EZ is not one of them. Nidalee and Jax are examples of decently made hybrid chars. They could be better but they work better than EZ.
There are just some champs when I see then being played I groan badly if they are on my team. Some champs aren't worth playing unless you are pub stomping. EZ is one of them.
They have fixed some champs from crap hell in my opinion. Eve is one. She isn't what I call the best champ but she is decent enough I don't get pissed if she is picked at least now.
Characters are only as good as the players that play them. Barring a completely analytical by-the-numbers assessment of a champion (which, by the way, I think is foolhardy, because it's much harder to assess the true strength of a champion by the numbers; positioning, game flow and many other harder-to-quantify factors contribute to champion viability), the best way to assess a champion's strength is how they are played.
Now, I don't know your personal philosophy on the subject, but I think that champions should be balanced primarily on higher levels of play; that isn't to say lower levels of play should be ignored, but balancing around higher levels of play should be the primary objective. No one argues that SC2 or any other competitive game is balanced around high levels of play, in fact, it would be foolish to cater to the lower end of the market.
So, I think your contention that Ezreal is weak is derived from the fact that you view him through the lenses of lower level play. Ezreal doesn't have the same overwhelming level of OP-ness he did when first released, but he can still be just as effective as any other carry in the right team composition.
This brings me to my final point: team composition. Tangential to this whole assertion that a champion is 'bad' is completely ignoring an entire aspect of gameplay: pick vs counterpick. I suppose you play a lot of unranked games? In many ranked games, the outcome of the game is determined at character pick. Many champions can be 'countered' by another champion's pick, at multiple levels.
For instance, Kassadin is a counterpick versus Nidalee, but not in a lane. A counter-lane pick for Nidalee would be Lee Sin. A counterpick for a Shen would be Janna, because you don't let the other team have Shen/Janna, because you'll lose the game all other things being equal. A counterpick for Karthus would be Soraka, and etc. I'm only mentioning this because my remarks about Ezreal's viability are made within the context of pick-counterpick. He would be, of course, way less viable against a team that had champions like Kassadin, Irelia and the like.
Finally,
Eve was considered crap a long time ago, and hasn't been changed fundamentally since. She's only considered 'okay' to 'good' now because the community has got a clue. Jax is a shit champion. If you want to relegate a champion to 'shit' status, it would have to be Jax. He takes too long to get going/fed, brings nothing to the table if the other team has any clue, and is too easily CC'd to death before he can make an impact. Don't take my word for it though, hop over to solomid and take a gander at their high-level guide for Jax.