I'm gonna be real with you, and I'm about to put a game that I absolutely love? On blast.
If we take away complexity but still demand a competitive game, we get something that leans towards what Project: M is right now. Project: M is TERRIBLE for this and how auto-combos are a snap. For a competitive game to thrive it can't be boring like that. Project: M is very easy to play due to auto-combos even without the need for wavedashing and L-Cancelling. That said, it's deep enough despite the flaws that I like it. Moving on.
Some characters are just going to be more technical than others. It's why Fox and Falco are only played by people who wanna put in the hard for for it. If you took away their complexity, what do you got? You've got Brawl mindgames instead and there's less technique and more reading your opponent. It's a good thing, but it's not the ONLY thing that makes a tournament-hype game good.
Me for example? I can do tech, but I am NOT a technical person on the level of spacies. I don't have the patience OR the skill yet for that, even though I like Fox and Falco as characters. So? I play Ganondorf and Sheik. I play Charizard and Roy in Project: M, I play Sonic in Brawl, I play Falcon in Smash 64.
Having the entire cast accessable and EASY to play (which is what I'm getting from what you're saying, correct me if I'm wrong or putting words in your mouth), is NOT a good thing. It breeds a boring, casual game, and IMO, it also breeds something for the inbetween players. And when you're inbetween? You're gonna wanna get better and to get better? You have to beat the people that are more serious about it. And if you can't? That's your own fault because your skills with your character aren't there. You are either playing the wrong character or need to learn to cancel your attacks, or become a GOD of reading your opponent if you're not good with tech skill.
Even in Melee you didn't lose your input simplicity. Every move is available to you. It's just HOW you use those moves that counts. Thus, the deeper mechanics that take us further. This isn't some super duper high barrier or something to break through. Get your *** kicked by some better players and you'll learn or give up, but above all else? Have fun. We all do at all levels of the game.
I currently consider Project M the (currently available) ideal version of Smash simply because it makes some of Melee's tricks either easier to do or at least apparent (like adding the flash to L-canceling).
And while I'm sure I often sound like I think everything should be absurdly easy, I really don't think that. Nor do I think that every character should be accessible and easy to play. However, I do think that the depth and entertainment factor in the game largely comes (at least to me) from watching a player's mastery of their character. Watching Sethlon play Roy, or watching M2K play Mario, or watching PinkFresh play Lucas - things like that are entertaining to me. Those players aren't just good at the "basics", they know their characters and their opponents, and outsmart them through application of their technique. I just think that the aforementioned technique was
too difficult in many cases, widening a skill gap in a way I don't personally feel it should be widened.
To kinda break it out a bit more: The first survival technique that takes some practice is teching. It's a key ability, and failure to use it will get you killed against even an average non-competitive player, but its timing window is generous (20 frames), and while it is strong, it doesn't make you invincible for long. It sets up mind games that stem from that skill - tech chasing and whatnot.
Past that, I'm going to put the L-Cancel as the next gate (though your mileage may vary). Its timing is much tighter (1-7 frames in Melee) than that of teching, but on top of that, it is always the ideal choice (as you never WANT more endlag on your attacks, at least in any case I can think of), and thus adds no decisional depth. It is simply a matter of can you do it consistently or not, and failure to do so will keep your play perpetually below that of an otherwise identically skilled player who has mastered the technique.
And at the end of the series of skill gates, at least for this example, we have wavedashing. It's a useful skill, it opens all sorts of options for attack, approach, defense, and retreat, and whether or not it is useful or vital depends on your character. However, it acts as a technical barrier for those characters who do rely on it (such as the spacefurries), which is a situation that I feel is not good design. Now, if it were available on a character-by-character basis (like double jump canceling), I may feel differently about it, as it would be more a matter of learning advanced tricks with specific characters, rather than learning which characters can best exploit a basic mechanic. Making it universal and yet so valuable for only certain parts of the cast feels, to me, comparable to making only certain characters able to jump out of shield (which is often cited as an issue for Yoshi, as he lacks this ability).
In summation (or at least, I hope this is what it sounded like), an advanced technique should be somewhat generous in its execution, and should be at least close to equally relevant for all characters (otherwise the metagame often becomes biased). Character-specific techniques are great (and at least at a glance, are what Smash4 is using a lot of with Shulk, Robin, and Luma, to name a few we've seen), and allow players to show off skill and mastery with their characters beyond that which your average party player could grasp. That kind of skill (which, indeed, may well end up favoring certain characters) is what excites me the most - it makes the technical aspect of the game attainable but not inhibiting, while leaving plenty of room to mechanically and strategically outplay your opponent beyond simple reflexes. In other words, the basics should indeed be basic, and those basics should, in my opinion, be enough to fight on roughly even footing with an opponent. The rest of a player's advantage should come from knowledge and skill with their character in particular.
And no, I don't like the campy metagame that developed around Brawl, but there are ways to fix that without relying on quick aggressive techniques - weakening defensive options is a great way to start, and that does seem fairly evident in the endlag on air dodges amongst other things.
I'm hoping that Smash4's options and mechanics are strong enough to facilitate a primarily aggressive game, easy enough that the hardest part of the game should be the mental part, distributed enough to give every character a fair (if matchup- and stage-sensitive) chance, and obvious enough for an "average player" to discover without any external help (whether it's shown in a video or just usable by CPU players).
