I'm glad that the conversation is civilized. I note your points but note that I'm not defending 3rd edition. In certain aspects, was an improve from AD&D (better maths, I do like feats as a customization option, etc.) but it came with his own problems. As I said, I tolerate it, and in some aspects I like it, but, while I begin to play when 3rd edition was beginning (2001, aprox.), I quickly pass to AD&D.
To me, it has his flaws but ultimately they were correctible and not so important at all compared to the big hindrances it brought (rules mastery, power creeping, etc). Power problems in AD&D came at serious levels, levels that, by the slow pace of experience advancement, almost never occur in my tables. Oh, yes, a level 5 mage was a real mess in a table, but when a wizard climbed to level 5, the rogue was already in level 9, so it does not bother as much*. I'm not saying that AD&D has not his own problems, and many of them were corrected in further editions.
That said, the difference between a skillfull munchkin player and a more light approached one conects with dissociated mechanics: you have to have a certain degree of rules mastery to be an average player. The average player is more munchkinesque in 4th edition. An average 3rd edition player (and I've played with many non experienced ones) certainly is not near as effective as a munckin one, because the powergamers were scarcer as it tends to be a game were rules and options were monstruously high. The vast majority of average players doesn't pose such a threat in terms of breakiness of the game, and you can play intuitively, without reading a single book, and be useful.
I don't know if it is the case outside my country, were D&D books are expensive and mostly in a secondary language (English is not as universal as you may think, no offense intended), but here most players don't know most rules. I'm a nerd, and I've been translating AD&D manuals since I had 16, but even I don't read as much further than the 3.5 Player's Handbook until very recent times, and I've played in three tables. I certainly don't remember all feats, caveats or exploits, and I've made myself very effective in campaigns simply by asking "I'll try to do X. Can I do this?". Mostly, I've used basic rules (my 3rd ed character was a crossbowman soldier, and shooting at long range, covering behind a heavy infantry guy, trying to capture or not to kill avery foe, sneak, sharpshooting, flanking, etc). In fourth edition, (I tried it in a few conventions) I had to know the warrior spells, and it was mind-boggling. I had to read the core books twice. I never could convince my wife to even try it (she played RPGs because of me, not because she is a fan, so she is very light hearted. And certainly she don't want to do homework to play).
What I'm trying to say is that to become an average 4th edition requires a level of metagaming mastery not present in prior editions, hence the dissociated dynamics as the core. Yes, in third edition, dudes that made their homework are table-breakers, and more of a problem than 4th, but they don't constitute the core of many tables. You can think yourself in that place and say something as "I make a descending attack with all my strenght, trying to make as much damage as I could", and the master say "throw 1d20", and internaly or externaly he decides which rule to apply, basic attack being the most common option, but also Power Attack, or grapple, or whatever it adjust more to your intentions. See? not metagaming skill needed: you actualy behave like you think your character will do.
*Think that defeating 6 (50 xp) goblins in 5th edition makes you pass a level. In AD&D, a goblin is worth 15xp, and you advance as a wizard at 2500 xp. "Farming" monsters was not an option. And the easiest way to adance? Treasure, and campaign experience. Magic treasure give experience. Learn spells gives experience. Solving problems give experience. Sometimes, this was through combat, sometimes this was with cleverness.
