Also let me emphasize that I operate under the assumption that the group is unified. So playing various styles in a single campaign is no concern of mine.
I don't agree with those that think the game can only support one style.
But, your assumption of a unified group would mean that it need only support one style /at a time/, which, as far as I understand the 'support only one style' position, is pretty close. The 'game can support only one style' crew are OK with a game, in effect, supporting a variety of styles, one at a time, through modules or whatnot, again, AFAICT...
I don't see how if the warlord ruins the game that I can sit down with someone playing the warlord.
A matter of tollerance, I suppose. As I've said before, I can't abide psionics. But, when I finally played in the odd 4e game that included psionics, I found them tollerable, not because they weren't still fish-out-of-water sci-fi rejects that had no place in a fantasy world,

but simply because they didn't jump out and dominate the game the way they sometimes could in 1e. They weren't good or fun or adding to the game, for me, but they weren't destroying it, either.
I'm not sure because I'm sure I'm not even aware of all possible styles. At launch though, 4e removed the simple fighter concept and the complex wizard concept.
Is 'complex wizard' really a concept, or is it a mechanic? The 4e wizard is a bookish fellow who's always adding to his spellbook (it contains his rituals), and memorizes different spells on different days. In concept, he's no different or less complex than the 3e wizard - indeed, conceptually, he's more complex, since he has both quick-recharge, and always-vailable spells, in addition to the traditional fire-and-forget. The mechanics, and thus complexity of the two classes aren't vastly different, but the wizard is certainly the more complex of the two. Similarly, while the fighter has some added mechanical complexity, the range of concepts the fighter covers is actually a bit more focused, ceding archers to the Ranger and a whole host of concepts it could never quite handle to the Warlord.
It also seriously stomped on the simulationist style of gaming. And I am not meaning to offend by saying that. I'm sure 1e,2e,3e as far too simulationist for many.
I certainly don't recall 1-3e as being 'too simulationist,' not by a long piece - imbalanced, sure, especially at high levels, though that's not the same thing. But, I'm not so sure I see the GNS theory as really working well when each is considered an individual and exclusive style, with games necessarily catering to one of the three (or one of the three at a time). Rather, GNS makes some sense when each is considered as an aspect - perhaps even a necessary one - of the RPG experience. RPG /are/ games, for instance, and no game could be totally un-gamist. And, they include Role-playing, which, quite irrespective of the gamist (mechanical) element, will include both some immersive role-assumption and some actor/director-like 'storytelling.'
I believe SOME things could happen at the same table. But when I say playstyle I'm talking more simulationist vs narrativist and those people don't even want to be at the same table.
I don't know, that's a much more extreme view that I can get behind. When I read the various articulations of GNS, I see in each 'style' an emphasis, at most, not something exclusive. In fact, I'd be hard-pressed to pick one and say I play exclusively in that style. I'll make gamist decisions to 'win' a combat, I'll make narrativist ones to move things along or keep from 'de-railing' a plot, I'll make immersed first-person ones when I'm feeling it. Similarly, a game's mechanics are the (gamist) rules of the game, /and/ the (simulationist) 'laws of physics' of the imagined world, /and/ the tools (narrativist) used to build a collective storytelling experience. Some games try very hard in their design to come down as firmly simulationist or narrativist, but they always end up being the other two, as well.
Sure, I could play the simple wizard and you could play the complex one. Nothing wrong with that if nobody at the table minds. Thats probably often going to be true. In other cases, it's likely to be a group decision no matter what. If I hate healing surges, it's not just that I hate them for my character, I hate them for all characters. Getting them off my sheet doesn't solve the problem.
Why can't you manage the same open-mindedness about someone using a fighter with dailies or healing surges as you can using a simple vs complex wizard?
I think the "dream" of uniting everyone at the same table is hopeless.
I agree, but I think that excluding a fairly small set of more extreme "my way or the highway" styles could result in the vast majority being able to sit at one table. In theory. My concern is that said small set of more extreme styles might well constitute a fairly large plurality - if not an outrigh, if un-unifiable majority - of WotC's player base.