This is a purely subjective idea, and I'm not sure its full formed (hence ramblings) but perhaps its something...
For S&G, I pulled out my 1e DMG or peruse the words of wisdom. As I did, I noticed something, odd. Something I haven't noticed for a long time...
1.) 1e is random, and its weighted against your PC.
Take a look at character generation. You roll 3d6 (getting a 3-18 split, heavily weighted toward the middle 10-12) for scores. By strict reading, those rolls determine your class (primes and requisites) and race (racial min/max) even your gender (min/max)! You rolled starting hp (leading to magic-users possibly having more hp than fighters!) and starting gold (possibly not even enough to afford good armor or weapons!) and magic-users rolled starting spells (via two contradictory methods, one in the PHB, the other in the DMG). If you were dice lucky (or a horrible cheat) you got the PC you wanted and he would survive the grist mill to greatness. Else, you got to try again when that less-than-stellar PC met his end.
Not all of your points above are accurate (I doubt that most campaigns use or used straight 3d6 in order to determine stats in 1E, that's typically an OD&D thing; stat mins and maxes can disqualify you from certain races or classes, but you'd need truly awful stats to be limited to one choice of class; the "two systems" of spell generation aren't actually contradictory, etc) but you're right that there is no guarantee in 1E that you could play whatever you wanted or that your PC was just as potent as somebody else's. You might be a fighter with low HP, or poor armor, or a magic user with poor spells. If you were smart enough and lucky enough to survive, that would change.
Even beyond chargen, you faced an essentially "random" world. Random encounters, random treasure gen, even monsters had random hp. Your PC had a random chance of getting lost, and NPCs had (essentially) a random chance of liking or disliking you. And that doesn't even begin to factor the still-random elements of D&D (Attacks, Saves, etc).
In practice, the game is as random as the DM wants it to be. Most of the game isn't random IME. The DM creates the adventure locales (usually dungeons) and chooses what creatures dwell there. While it is certainly possible to do that using random tables (provided in the DMG) that is mainly intended for solo gaming.
All of this "randomness" puts the PC typically behind the eight-ball. Most monsters (typically) had more hp, better attacks, and more powers than any PC could possibly bring to bear. This lead to the second observation I noticed...
How do you figure? The monsters have 8-sided hit dice and no constitution bonus, so the fighters (10-sided HD+CON bonus) have more hit points than monsters of equal level. Often
many more. The monster attack table is better than the fighter table up to about 10th level/10HD, but monsters get no hit bonus from Strength while fighters do. Add in things like weapon specialization and the much greater likelihood that a PC fighter has a magic weapon or armor, and PC fighters hit better, do more damage, and have more hit points than the monsters that they were fighting.
As for powers, even a mid-level spell caster has a lot more versatility than most monsters in 1E. Most creatures don't have any magical powers at all. Only Really Bad Things (demons, devils, beholders, liches, a few others) have a huge number of magical abilities.
2.) The trade off for power is reliability.
Why does 4e's Power System Soooooo offend old-school gamers? Because it breaks the most important principal of magic and mundane power:
Magic is powerful, but unreliable. Martial power is reliable, but not terribly powerful.
I'm definitely an old school gamer, but I'm not "offended" by the 4E powers system. I don't have a very strong opinion about is as I've never played the game.
There are, of course, exceptions to this axiom. Still, compare a fighter with a great sword NOT to an attack spell like burning hands, but to Sleep. Sleep ends a fight before it can begin. Sleep targets multiple foes. Sleep is a TPK in the hands of a foe. However, Sleep is a saving throw away from uselessness.
Actually, that's wrong. In 1E Sleep doesn't allow a saving throw. However, your point is still valid. There are plenty of things (polymorph other, hold person, stone to flesh) in which a saving throw completely negates the effect of a spell.
No second effect, no damage nothing. Save Negates. If the creature(s) save against the spell, its done with. Compared to a fighter, who might not be able to end a fight in one round, but he can continue to try to attack every round until he hits with no penalty.
4e changes that balance by making magic more reliable, and making martial more powerful. Its better balanced, but a major shift from this principle which has been with us since the beginning.
It is my belief that these two things create the greatest shift in D&D's style from 1e - > 4e (and each version of D&D in between, the changes show up slowly). 4e bridges power and reliability. 4e encourages a "planned" world where PCs create their characters without a single die roll and allows them a variety of "balanced" choices. 4e (for the most part) removed random encounters, random hp, random treasure for a more "why am I putting X here" approach to adventure design. Lastly, 4e tries to balance the needs of the players against the needs of the DM (1e was squarely in the DM's corner, 3e sat down with the players), all of which can been seen in the evolution of editions (esp latter-day 2e and latter-day 3e) from that "1e feel"
That's my theory. Feel free to pick it apart.
I think it's wrong to suppose that 1E is "squarely in the DM's corner" and against the players, as the players and the DM are not enemies. The 1E DM (I presume this is true for all the other editions as well) wants to see the players triumph - but he doesn't want to give them their triumph on a silver platter. An earned victory is much more to be savored than an easy victory.
As for 4E's way of doing things, it seems like it might make all the classes seem more similar to each other, but (as I said before) I have never played the game.