You skipped the time period where it was Little Mac for a brief bit.  It's just silly. 

Bloody hell, I hate the whole wave-dashing/etc rubbish. When a game forces you to learn tedious exploits just to be competitive, that game is fundamentally flawed.

And it's just sad when players become so entrenched in these exploits that they can't play without them and demand their return.

God forbid people ever have to, you know, learn new gameplay mechanics and movesets.

Saying that the game wouldn't be competitive without wavedashing is like saying Mario Kart 8 can't be competitive without fire-hopping. Heck, Smash 64 never had any form of wavedashing, yet it has grown in popularity in recent years.

Wavedashing would not make Smash 4 more spectator friendly, because the game would still be flawed at its core. The low hitstun prevents creative combos, instead forcing people to use the same guaranteed follow-ups over and over (such as the now well known Diddy Kong d-throw into up-air chain, and Shiek's f-air chains). The extremely low shield stun makes shield pressure that doesn't involve projectiles unsafe, which is why shield grabbing into follow-ups is such a large part of the metagame. The new ledge mechanics prevents edge guarding which is why you will often see professionals allow the opponent to get back on the stage, causing the match to slow down every time someone is launched yet not KO'd.

As it looks right now, there is nothing to suggest that Smash 4 won't end up like Brawl. Both games heavily reward defensive playstyles, which is why the same people who were Brawl professionals are Smash 4 professionals today - due to how well their skill in this particular playstyle transfers over.

I would also advice everyone to stop acting like Nintendo honestly care about the Melee crowd. Project M, a highly successful Brawl mod made to make the game more similar to Melee, was removed from Apex the moment that Nintendo became an official sponsor. This was despite the fact that the mod was the second most popular Smash game in the competitive scene and despite the fact that it officially required a Brawl disc to be played. Not only that, but the most prominent Smash streamer, vgbootcamp, recenty stated that they won't stream any more Project M tournaments and remove all PM content from their youtube channel because Nintendo might sue them. And let's not forget how Nintendo initially tried to stop Evo from streaming Melee during Evo 2013, only allowing it after receiving massive backlash from its fans.

As for the Gamecube controller support, which supposedly was made to cater to the Melee crowd:

1. As good as all Brawl professionals prefer/preferred the GC controller.

2. Wired controllers are required to run a tournament without wireless interference all over the place. Since the large majority prefer the GC controller in Smash tournaments, it was the obvious choice.

Fire-hopping is a flaw in Mario Kart 8, just like wave-dashing and other exploits are flaws in Melee.

Games are not supposed to have exploits, that's why they're called exploits.

Well, my point was that neither wave-dashing nor fire-hopping was required for either of those games to be competitive.

Still, exploits are found in every sport but that doesn't mean that all of them should be banned/punishable. Especially not if they are well-received by the players.

I'd contend that Melee's exploits give a bit more of an edge than fire-hopping, particularly given the more random nature of Mario Kart.

The fact that they tried to put them back in with Project M speaks to me of a dependence.

When that which is new and different is spurned and the comfortable old ways are rigidly adhered to for their familiarity, that's when stagnation tends to occur.

They didn't try, they succeeded. And it's not a matter of dependence, it's a matter of preference. If given the chance to add a well-received movement option, why decline that opportunity? It still doesn't change the fact that Project M would be an excellent competitive game without it. I would even wager that if Project M was initially released by Nintendo and didn't feature wave-dashing, it would have been more successful than Project M ever was.

As long as there are various different gameplay styles working in a rock-paper-scissors fashion, stagnation is prevented. Some people claim that Fox will be the death of Melee in the long run as other characters lose their viability, which is a legitimate concern. We are not there yet though, the winner of Apex 2015 was a Marth/Falco player and Marth is widely considered a good counter vs Fox. Especially on Final Destination.

Smash 4 still has the potential to become a competitive game of great variety. But considering how successful Zero has become with the highest ranked character, Diddy Kong, there is currently nothing to suggest that Diddy Kong won't become the new Meta Knight. And even if he doesn't, variety in gameplay doesn't necessarily correlate with becoming successful as a spectator sport.

It becomes preference coloured by familiarity though, and people become closed off to any and all change because the old is held up as the gold standard from which any deviation is considered a flaw. Playing only a 14 year old Gamecube game for the rest of eternity sounds stagnant to me.

By all means, enjoy the old, but intolerance of the new is an unhealthy attitude.

Supposedly wave-dashing is a feature not an exploit.

No, wave-dashing wasn't a feature, it was something that you were able to do because of the air dodging mechanic in the game that allowed you to use it to increase your speed on the ground.   If it's because Sakurai knew about it, well, he did know about it, he just didn't think that anyone would use it since he was advertising it to be a party game rather than a competitive one.  L-cancelling was a feature that existed in both Melee and 64 if that's what you were thinking about.