I was in debates (including people in this thread) in which a key point of contention was the idea of characters not being good at things.
A simple example was that a rogue might be much better at climbing a wall, but everyone should have a decent chance to climb the wall.
Thus everyone gained }+1/2 level to everything.
In 5E, you can be a 20th level character and still have a +0 in a variety of skills (and even saves)
But still have a decent chance of success (eg 30% against DC 15, which seems to be the median DC for the system).
The real difference, as I see it, is not the mathematics of bounded accuracy.
The difference is the implications for genre and story of the way it is implemented. 4e is designed tightly around the "tier" structure: combat abilities, paragon path and epic destiny descriptions, the Monster Manuals, the example traps all work to reinforce this. The result of all this is that - if you play to these defaults - the PCs
will progress through the "world of D&D", from villages threatened by kobolds to combatting demon lords on the Abyss.
The fact that, when you look at the 4e mechanics, an epic wizard can also trivially scale a kobold barricade, or trivially intimidate a Greyhawk street thug into handing over his loots, is (within the scope of this design) a relativey minor side-effect. To the extent that it comes up in play, it is minor flavour. To the extent that you want to make this sort of thing a major focus, it would be the epic wizard wiping out a kobold stronghold single-handedly, or taking control of the Greyhawk thieve's guild, and it would be resolved as a skill challenge with level-appropriate DCs (and so the question of how easily that wizard can scale a single barricade or intimidate a single thug would not arise as part of the resolution).
5e does not have the same default story structure. There is a deliberate intention that the mechanical equivalent of 4e's pargon heroes might have to engage single differentiated kobold barricades, or single differentiated street thugs, in the course of meaningful action resolution. That's not a mechanical change - 4e also has single differentiated barricades and single differentiated thugs that are relevant to high level PCs (eg the barricades that Dispater erects to trap his foes, or the thugs that Orcus sends out to kill intruders in Thanatos). It's a story change - a change in the character of the fiction, and the way it is meant to be handled, and to change or not change, over the course of the game.