To me this thread is interesting because it reminds me of a large argument I got into on these very forums about combat/roles and the emphasis of 4E on the grid and tactics.
The point I made back then was that on occasion I have wanted to play a character that is (readying myself for horrified gasps) completely incompetent in combat. So when I saw that I really couldn't create a spindly little cowardly wizard who really only shined in certain key situation, I was bummed by 4E.
Note that like many have said here this is entirely a style thing - I get that some people wouldn't get why you would play someone who's no good at the "important part" of D&D.
The 4e answer back then took two forms, basically either "You are stupid for wanting to do that" or "you can do that, just ignore all your character's powers"
Roles will always exist in any group of people, whether real people or fictional people. For me the problem with roles in 4e was that they weren't really roles in the general or dramatic sense...they were the COMBAT roles.
They didn't have a role called "Con Artist", because it didn't apply to combat. I am not saying you couldn't roleplay a con artist, but the role system was essentially based around combat.
Again going back to style, I think that one of the things many groups don't do anymore is a schoolyard thing...they don't know how to take turns.
Raised on AD&D, I was more than happy to watch as the fighters did their thing, knowing that they would be happy to sit back when it was my turn to shine as my thief snuck about....I can't tell you how weird it was to read earlier in the thread when someone basically said it would be terrible to have a rogue that wasn't in there stabby stabbing all the time. I'm old, and I remember a time when you might get a couple backstabs in, but the rest of the time you'd better be hiding.
It takes a great DM to make taking turns work, but we had great DMs.
The design assumption in 4E (and possibly other editions) was that no one would ever want to be idle and observe...which again, I get and it's a noble idea, but once you make the assumption that everyone MUST be active at ALL TIMES, then you're going to need to turn everyone into a combat contributor and have tons of combats, or have that ghastly (opinion) skill challenge system where everyone can find SOMETHING on their list to shoehorn into a way of getting through.
In combat, you could paraphrase The Incredibles: When everyone is great in combat, no one is.
I understand the dangers in terms of boredom or one-player hogging the game, but I want to get away from what I saw in my attempts at 4e, which was everyone looking at their cards to figure out the way that THEIR CHARACTER did Xd6+Y damage and moved someone two squares.