I might define the term "moving on" to more specifically mean, "Achieving a more accurate result of an abstracted simulation with fewer calculations / fewer variables / clearer results / more consistent application of existing mechanical principles."
The "science" of game design is pretty straightforward, actually. Numbers can be manipulated in any way necessary to produce a "proper" range of results, based on inputs.
The thing about an RPG is that we want as accurate a result as possible with as few inputs as possible.
That's where the art comes in. The art is knowing what result you should expect based on inputs . . . and then defining the least intrusive, fewest-calculation way of achieving that result.
There's no question that there are ways to objectively rank rules "effectiveness." Different mechanics that represent the same basic outcome -- "Your character has taken damage" -- can be more or less effective based on desired result.
I think in most cases, when we prefer a newer system to an old one, it's because the changes to the system have improved the process for achieving the result.
One of the strengths of the d20 system is that at its core, it is a very effective "shorthand" for simulating a wide variety of situations. A d% / roll under system is more granular for certain . . . but do we really care that someone with a skill rating of 77 is in fact 2% more likely to succeed at a task than someone with a 75 rating? In most "real world" situations that matter, that 2% chance is trivial.
