Melee was overplayed because most other game in most other genres never take 7 years to get a sequel, it's time to move on to new things, we've played enough of Melee, great and epic as it is.
Lack of reward for effort? I think this is a matter of opinion as well, and I strongly disagree, while the game speed has been lowered, it doesn't mean that you don't have to time things, learning to time perfect recoveries, Edge guards, Spikes, Chain grabs and more still takes a lot of skill, and takes time to learn and discover, I think anyone that says brawl isn't developing and changing in every second is blind IMO.
it might take less time to get "Good" in brawl, but that doesn't mean you've reached a ceiling, we've barely even begun climbing, people are learning, adjusting and improving all the time, and a new player will not beat a veteran, if the veteran has more polished skills. saying that Defense is too strong or that noobish moves are too strong just shows you didn't practice enough(not implying you said it, but a lot of people do say it).
the reason I like the fact brawl is more accesible, is because it's caused my community to triple itself in no time, more and more people are interested in the game and in learning it at high level, people can actually understand what I mean when I explain DI,RAR and etc' to them, and people don't spend years learning one small in-game abuse that you're completely doomed if you're unaware of it.
Fighting games in general are moving towards the "Simplicity" notion, timing windows are enlarged, tech demanding things are removed\readjuste, and more. I think this is a good thing, cause it lets you concentrate on the important parts - playing better, smarter and punishing your opponent's mistakes. and not just showing off the fact you have inhuman tech skill, tech skill should stay as a demand for some characters, not all.
basing a metagame over in-game abuses that are hard to learn or understand completely kills off the ability to understand the game for a bystander, and also takes away the fun of learning it, since you need to concentrate on a specific skill, and not on learning the game and usefullness of each move and strategy.
wavedashing and L-Canceling not only broke the intended balance for the game, but also completely decimated the usefullness of some moves, while infinitely boosting the usefullness of others, now that every aerial keeps the intended amount of lag, and you have to learn to work around it, and you're forced to use a variety of moves or other anti diminishing strats, it makes playing properly much more of a mind skill than a hand skill, which is a good thing.
In melee, a falco player that knew how to SHL approach and how to shine jump dair, and knew nothing else, but could perfectly perform the above, would still be able to cope with players much smarter than him, only by abusing the same strategy over and over. diminishing returns kills that ability, and making most techniques much more obvious and\or easy to learn, takes the competetiveness of the game to the next level.
the more people can and want to compete - the game is more competetive. the easier and more accesible the controls are - more people would like them and want to compete. the more understandable the game becomes to bystanders - more people will want to try it, and will find it accesible.
all of this does not in anyway mean that the game has nothing in it to learn, or has no depth. because performing perfect DI, Edge hogging(which now means falling to the edge at the exact timing of the opponent's Up+B in most cases, much harder than Melee), Comboing(Less hitstun = harder to combo = combos are harder to discover and learn. hard = good isn't it?) and more, still takes a ton of skill, and the better the opponent, the more skill needed and the more you can improve by playing.
and like I mentioned before, Tech demanding stuff are still there, but on spcific characters. try to alternate grabs between ICs at a high percentage, I dare you. try to memorize the exact timing of the IC's chain for each of the 39 characters, I dare you.
but that's just it, the depths and things to work on are there, but in diffrent forms