Sorry, but one-shotting, learning curve and skill sound weird together in one sentence. If you can oneshot people, there is no learning curve and no skill per definition.
My experiences back then, even when fighting chain ccs, bunnies and skippers was different. Sure, you could die almost as fast as now, but at least you knew what hit you and if the guy was cheating or not.
The fights against non-exploiters were a lot more fun back then and more tactical, because you could actually do something by moving, timing, reacting and watching the enemy (and most cheaters had a limited attack sequences).
Talking about the period between 1.4 and 1.6 here. With 1.6 the "memory optimization" and rubberbanding introduction, the fun started to dwindle and it got more and more luckbased. And i must admit i did not play all classes back then, but had a melee, caster and ranged.
In the above posts the interesting thing is (i agree with most of the analysis, except the points i mentioned), that people still mistake experience for skill. If you find out all the bugs, exploits and weaknesses, that is experience. Skill would be to react and apply the tools given. Had most of the players back then been more "skilled", there would have been more variety in attack sequences
I don't agree about it being irrelevant. Especially when it comes to the technical side of "optimization" and anti-exploit mechanism. They definitely require to be looked at, because the "optimization" back then was done with locally distributed servers in mind. What worked back then, dees not necessary work now (and whoever remembers the deadly waters of Tesso can argue, that they even worked back then). A second lesson that "could" be learned, is how you decide the pace, learning curve and balancing of battles and how you achieved it back then and now. So no...history never becomes irrelevant.