It's considerably more than just d20 roll high though. The skill systems are virtually identical. The character stats are identical. Even most of what a character does, day to day, hasn't changed all that much. As far as "not being able to convert", there's equally as many DM's here who are perfectly willing to show you how to convert your concept into 4e. The only time it's really an issue is when people absolutely insist that class is some sort of in game construct and that a fighter MUST BE a fighter or it's not the same.
Pemerton's only real deviation here is in the skill challenges, which can play as large or as small of a role in 4e as you wish. And, it's not really a deviation, simply extrapolating what's already there.
Hey, if you want to complain that 4e presents itself badly? I'm 100% right behind you. Heck, all you have to do is read between the lines and you'll see how much 4e is going to be in 5e, just spun right and everyone will be eating it up.
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Since we're talking about what we don't like, I'll add this. There's a reason I don't like all the rules to have a 1:1 relationship with the game world. It's too limiting. I don't want the mechanics to define my game to that degree. I want more freedom, both as a player and as a DM.
Earlier in this thread (or one of these anyway) someone talked about a character giving a speech and failing. The DM narrates that a rainstorm shows up and rains on the PC, thus spoiling his attempt. To me, this is fantastic. I want this. For some people, it's apparently immersion breaking because a failed skill check had an in game effect that was not related to the check itself.
To those people, my answer would be simple. Don't narrate it that way. Use the dissociated mechanics in an associated way. Only narrate from the basis of what the character could do. There's no problem doing it that way. Avoid a couple of the more problematic powers and you're good to go. AEDU can easily be explained in the in-game fiction most of the time.
But why go back to mechanics that are so limited? Sure, you get what you want, but, I get left in the cold. Broader, more easily applicable mechanics make everyone happy. So, if you want your effects to be deep immersion, go right ahead. That's your choice. But, why is my choice to grant players more authorial control through the mechanics so bad?