You are greatly overestimating how easy it is to please everyone. They do not have infinite time and infinite money. At some point they have to pick a direction to move in and make it as good as they can.
Also, for how much people love melee, I think it's easily the least accessible game in the franchise, for a lot of the reasons competitive players love it. Not being able to grab the edge backwards, no sweet spotting the ledges, the high speed of the game, and especially that old style of air dodging all make that game super intimidating to new players. Try watching someone who has never played smash bros before play melee and then brawl. Specifically, observe how many times they accidentally kill themselves. The difference is actually quite striking.
Competitive players criticized brawl for taking a lot of control away from players, but I think newcomers would probably report feeling much more in control of brawl, as counter-intuitive as that sounds.
I think he's more on par actually. I don't post here much, but in my life I've played Smash at two points. When I was 7, playing Smash 64 at my cousin's house, and then this past year in Japan. Starting out with 64 again every day (playing with a player who does tournaments), then into Melee, and finally into Project M (And occasionally Brawl if we were unlucky) every weekend.
This may be contrary to what I'm trying to prove, but from switching between Project M & Brawl, I noticed in insane distance in what I was capable of. I could actually
win in Brawl against my friend (Again, I want to stress the difference in skill level. He plays every day every summer and at school. I've played once in 10 years) whereas in Project M I
might be able to take a stock or two, maybe three if I was lucky. That didn't make me quit - that makes me want to get better and play more.
Finally, going back to Melee being difficult and turning away newcomers with that and how it relates to Smash 4 - I don't think that's accurate at all. If they are COMPLETELY new to Smash, they won't have anything to compare it too and most likely won't quit. If they AREN'T new, then they'll be playing against those of the same skill level if the ranking works (It's a ranking system problem if it doesn't), and at local bouts it's even easier to coordinate skills or have a good time.
All in all, a new Smash being difficult is completely meaningless to scaring away newcomers in my opinion. Comparing it to another genre, Halo, Halo 2 had HUGE emphasis on individual skill and was the biggest online titan of it's time on consoles, even with glitches in matchmaking that weren't used in competitive. Halo 3 deemphasized skill yes, but it also grew tremendously, including the competitive scene and advertising helped by that. Once the game switched away to less skillful additions in Halo Reach and 4, that was when the population started plummeting.
Also, one last thing for thought. Games balanced at the highest level are fun and work for everyone. Examples of this being Dota 2 and (to a lesser extent since the patches are more often), League of Legends. Everyone's happy this way - the competitive players have a game they love and that works for them, while the more casual players have a game that works just as well and the perceived "imbalances" don't actually come into play at their level.