Even though I essentially started my relationship with Forgotten Realms with the 3.0 FRCS (which is then my own "year zero" with the setting), I wholeheartedly agree with you.
I think basically all the famous settings became a success at their first iteration? So from a gaming point of view there is no need to advance or update the settings, if it worked great at that time then the best way to play it, is to play the original version of it. Of course from a business point of view, they want to release new books, but they could be "horizontal" expansions instead of historical advance (i.e. new places instead of new events), and of course they could be rules edition updates. I don't want to be forced to move along with the ludicrous FR metaplot just to get FR updated to 5e rules...
And by the way "updating to 5e" does not mean that every setting must allocate every single race or class or whatever is in the 5e PHB: a campaign setting gets its strength and personality from what exists in its fantasy world, including player character's stuff. If you force a new iteration of the setting to allow unprecedented stuff only because it's in the new edition PHB, you dilute and bastardize the uniqueness of that setting. It's the new edition which should support settings, and not settings being changed to support the new edition :/
That would be a great idea actually.
3.0 is a good baseline for FR, grey box which I heavily prefer for nostalgic reasons also.
The timeline here is even helpful, you do not collide so much if you take one or the other if they are 100 years apart. So everything has two sides at least like always.
But compared to other settings FR is so much more forgiving, they say eberron is the maximum kitchen setting, but that is not true FR definitely is more kitchen sink, because in eberron everything comes with a twist (and somehow has to) whereas in FR it may come with or without twists
Original or blue box is a good baseline for greyhawk and in contraire to others I do not dislike the wars box, it offers the closest to some official (but easily to modify) canon. Wars just isn't a good baseline.
Ravenloft has several possible starting points, black or red box and the ravenloft timeline is very very precise, plus it is not putting up dependencies. Additions of domains (or vanishing of them) does not hurt much, because in ravenloft nothing (and everything) is connected, due to domain borders.
The original feel of Ravenloft and Darksun needs something which go beyond most fluff (canon), namely crunch (mechanics) which are true to the original mechanics purposes, e.g. power checks for Ravenloft,
weapon and armor of inferior material for darksun, whilest reflecting this inferior material ! mechanically because you can tell me all night long that the dagger is made from bone, it is when it breaks that it has impact. Also especially DS needs some hefty restriction in terms of damage resistances, feats, easy transportation, easy nourishment, and tricks like having a weapon at will. Also some classes are totally different (Bard), or won't fit at all (Paladin).
And no, the big critics always seem to come from people who think integrating dragonborn gnome paladin monk sorcerers into DS is more worth than to be classic, in other words
And by the way "updating to 5e" does not mean that every setting must allocate every single race or class or whatever is in the 5e PHB
like you wrote but without the not seems to be a big credo especially for modern players. For us old school grognards this is like a child which cannot decide whether to put sugar, salt, ketchup or mustard onto their meal and thinks better to take all so it cannot go wrong. Of course the meal gets bland by it.
