My point was more narrow, I think, than what you've taken it to be.Every edition did that, it just did it with varying degrees of effdup class balance, mechanical dysfunction, and smoke & mirrors. 4e just did it with less of the first and more of the last.
I was simply saying that the growing numbers on the PC sheet in 4e serve a purpose - namely, in conjunction with the published Monster Manuals they support a very clear "pacing", not at the encounter level or even session level but at the level of the campaign arc.
Eliminating the level-bonuses on the PC and NPC/creature side obviously won't change any of the maths of resolution. But it would destabilise this default arc. Whether that would be good or bad is of course a matter of opinion.
You must have played a different 4e from me! 4e makes the "laying waste to many foes" easy to set up, using minion and/or swarm rules.The desire to keep lower level monsters relevant lies, IMHO, in the genre convention of the mighty hero or wizard laying waste to many foes.
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So every edition tried to do it.
And every edition failed.
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4e, of course, failed due to the illusion of the Treadmill
I'm also not sure what you mean by "the illusion of the Treadmill".
What's the illusion? Everyone knows that the numbers getting bigger on this side are matched by the numbers getting bigger on that side. Everyone knows that the basic maths of resolution is not changing. That's part of what makes the game run smoothly.
The "advancement" in 4e occurs (i) in the fiction, as broadly set out in the PHB and DMG descriptions of "tiers of play", and (ii) in the range of non-to-hit-and-damage effects that are available to PCs both in and out of combat (eg stunning vs dazing, dominating, flying, teleporting long distances and crossing planar boundaries, etc).