There is no such thing as a 'best RPG possible.' A Startrek holodeck wouldn't qualify, the Matrix wouldn't qualify.
An RPG is a system for portraying a world, and sometimes building one as well. And then for building and portraying individuals within that world.
I certainly agree with the first sentence of your first paragraph, given that I don't think I agre with the first sentence of your second paragraph.
I don't look to an RPG as a system for portraying a world. I look to it as a system for enabling protagonists (the PCs) to face challenges (situations/scenes/encounters) and to find out what happens - to the situation, to the protagonist. The world/setting is a backdrop for this, not the main point of play. And the protagonists matter because they are
protagonists - I'm not interested in them just as individuals (eg I don't generally care what their favourite dessert is, or the name of their first pet as a child).
That's not to say that
no RPG can be about portraying a world, and individuals within it. I know that some players like to play RPGs that way. I'm just not really one of them.
the complaining for 3.X was less severe and far far less sustained than 4E. It will be 6 years in June since 4E's release and the whining has not really abated. It has increased,to a degree, BECAUSE 5E has been announced.
My impression is that, before and leading up to 4e, the majority of the complaints about 3E came from those who played it, whereas when it comes to 4e, most of the complaints come from those who
don't play it.
This assymetry in what I perceive as the source of the complaints makes me see the situations as assymetrical more generally.
To many fans of particular editions, when faced with an update or redesign, there are always the lurking questions "Well, if you weren't satisfied with D&D before, why stick with it and change it? Why not play something that fits your needs better?"
This isn't all players, clearly, but there are always some for whom those questions are important. And who's to say they're wrong? If D&D isn't scratching your itch, why continue to play it? Why demand a new edition other than reprints?
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Why are you a D&D player if you wanted changes this massive? Why not play another game that fit your desires better?
I think that's a relevant question. And I suspect part of the reason is product identification.
In my own case, I stopped GMing AD&D in 1990, and started GMing Rolemaster instead, for all the same sorts of reasons as D&D players from the late 70s drifted to Runequest, HERO, Chivalry & Sorcerery, etc: richer PC builds, richer and more evocative action resolution, etc.
In 2009 I stopped GMing RM and started GMing 4e because finally D&D had become a game whose PC build and action resolution mechanics had the richness and evocative feel that I was looking for,
and didn't have some other baggage that I had come to find frustrating in Rolemaster (and comparable systems).
It's not as if material produced for D&D in the intervening 20 years was irrelevant to me, however. I used plenty of B/X, AD&D and 3E material in the course of running my RM game, and still use plenty of that material for my 4e game. (In both cases, I rework the mechanics, either in advance or on the fly.) It's not about product identification. As [MENTION=93444]shidaku[/MENTION] posted above, it's about the fantasy tropes.