And our "old system" was pretty new.
The "modern" Canadian army was born of the Cardwell Reforms of the late 19th century. The Navy had a bit older and better system: even in the 8th century promotions, for officers, were based on examinations for competence, for example, while the, in the 19th century, the army still had commission by purchase.
But many of our "systems" were millennia old - we've understood since classical times that an element of about 10 soldiers is about the maximum that one person can control. Think the Roman decurion. 10 of those elements could be controlled by a well trained, seasoned leader: a century ≈ a company (nine sections) which has been a standard military unit for centuries.
We have some bench marks. A battery/company/squadron (75-150 soldiers) can be commanded by one middle ranked leader (an officer) assisted by numerous junior leaders. Several companies - less than 10 (the number of digits on our hands seems to equate, roughly, with the upper limit of anyone's reasonably manageable span of control) - form a fighting unit which needs a more seasoned leader and a number of battalions, etc, etc, etc: Corps - LGen; Div - MGen; Bde - BGen; Regt/Bn - LCol; Bty/Coy/Sqn - Maj; Pl/Tp - Lt ... as the Commonwealth armed have/had it
Or: Corps - LGen; Div - MGen; Bde - Col; Regt/Bn - LCol; Bty/Coy/Sqn -Capt; Pl/Tp - WO ...as some European armies have/had it.
What do we need below Pl/Tp?
What is the appropriate rank for a soldier who is young enough but also sufficiently experienced to be a tank or rifle section commander?
What is the right rank for the 1st level junior (apprentice) leader? How long, in a 21st century army, does it take to get a soldier from "trained" to junior leader?
What is the right rank/age (experience level) for a Tp/Pl 2IC?
What about specialist leaders in Artillery, Engineer and Signal units? Are Officers or Warrant Officers better suited for many tasks in those corps?
What about staff officers and NCOs in units and formations and national HQs? What is the role of staff schools and colleges - for NCOs and officers? Is there a really a "command" course? Should there be? Does the Navy have the right idea with Sea Command examinations?
How should we measure fitness for promotion and for certain kinds of employment, like command? Should enlisted ranks be tied to trade level? Does the RAF system of "technical" NCOs who are different from "leadership" NCOs have merit?
I think we might be due for a review.