We have different definitions of skill, apparently. Pushing the 1 key every 3.5 seconds or so is no more skillful than saying "bang" out loud every 3.5 seconds or so. There's really no skill to it to speak of. Letting the game handle that for you (and more efficiently, at that) opens up room for you to be doing other things instead.
For example, if I went to Ifrit right now on my PGL, I could do things like popping Raging Strike, Ferocity, and Blindside while I still only have 1500 TP in preparation for a 3k TP Victimize. I know that all of those abilities will stay active until I have enough TP to do the attack, and then I can use them again sooner for a different attack. If I tried to do that on ARC, well, I can either Light Shot and waste the buffs, or Barrage and hope it does significant damage. Yes, I realize ARC doesn't have a native 3k TP skill, but even if it did, you wouldn't be able to do what I'm talking about with the current setup. On the other hand, even on my PGL, I might mess up and hit Light Strike instead of Victimize, thus wasting my buffs, so I have to actually pay attention to what I'm doing.
Of course, that's not even getting into the animation lock discussion. It's well known that LNC is basically the favored class for Ifrit, but your vaunted Light Shot is why ARC is the bottom of the barrel. At least the other classes can continue their auto attacks in the seconds leading up to Ifrit's attacks, whereas ARC has to be careful on its Light Shots. Note that, in this case, "be careful" actually means "stop attacking."
I'm not advocating "watching [my] TP bar fill up and hitting a weapon skill." I'm advocating using some preliminary buffs while the TP fills and damage rolls in, then starting in on the combos while watching my aggro. It takes just as much skill; we're only just now getting class uniqueness; combat will be about the same level of activity; and I expect ARC potency to go up, if anything. The fact is, ARC isn't "hard" now.