Isn't that largely what the Warlock was trying to be?
That was definitely more the case with the 3e Warlock as compared to the 3e Fighter, which I think is part of why it ended up being really popular. Fighter chose a bonus feat at 1st level and Warlock chose a single invocation at 1st level. That was it. You could easily jump into the Warlock without having any real understanding of how D&D spellcasting mechanics really worked, spend every turn using your default attack and the class would still work.
That's why I was a little disappointed to see the 5e version become more complex with the addition of cantrips and spell slots (of which there are dozens and more varied than 3e invocations. They don't even get Eldritch Blast automatically anymore. They gave the players a lot more choice in how to build their Warlock.
Meanwhile the Fighter class got *fewer* choices compared to 3e.
But you've hit on the point I've been trying to make...the Fighter is simpler in that there are less decisions for character build. I don't think that's a problem. I also don't think it limits the Fighter to being a "simple character" just because the class is simpler. It depends on what the player wants and how they play the character.
My issue is that those lack of class options is tied almost exclusively tied to the only class that really does non-magical warrior. Want to be that guy? Better be happy with only 1 decision point at first level, all of which are focused on how much more/less damage you do/take.
Want to play someone who just blasts stuff with energy? The closest you get is a class that also saddles you with having to choose a greater power to bind yourself to, a couple of damage/utility spells from a dozen options and another couple spells from a list that's even longer. Also, don't foorget that you have to specifically choose the blasty spells. They aren't assumed, and you can easily build a character with nothing but utility spells.
Heck, I'd be thrilled if D&D introduced a new class that was pretty much a non-magical warrior, but with some more utility in the other pillars. Call it whatever you want. Unfortunately, this has tended to be a divisive thing whenever it appears in D&D.
I mean, in my experience, the "social pillar" of the game is as much about how players play their characters as it is about CHA and a handful of skills.
Not entirely. Often times, being able to do stuff like speak/understand rare or unusual languages, being able to make decent knowledge checks related to the matter at hand, having useful utility powers, or being able to perform tricks like inducing various states of fear/charm/confusion can help where a simple Deception/Diplomacy/Insight check would not.
One reasons I really like Know Your Enemy is because it gives the Fighter an incentive to actually stop and at least talk to/interact with something. As mentioned before (or was it another thread) I really think it would have made a great 1st level Fighter feature.
And then there's exploration.