My responses in italic. Honestly I kinda hope Nintendo don't listen too closely. Perhaps it is just me but I find that characters with extensive combo games are less fun and it's difficult to get hype about being someones punching bag.
There's also some other opinions of various things like characters and etc. But many of them weren't consensus.
-There's a few melee players who obviously think L-cancelling should return, but most top players (of both melee and smash 4) think the decreased aerial landing lag is enough and L-cancelling shouldn't return
-There's a consensus Ganon is a much better character than in smash 4 or brawl, but some still don't think he'll be good while others think that the lack of landing lag on his aerials might be oppressive into certain matchups.
-There's a consensus Ridley's Down B is a pretty good move (it lands on frame 29, less than half a second of startup, and you get a free stock off of landing it pretty much 100% of the time, like a disjointed version of rest). Some seem to think he'll be bad because his hurtboxes are easily abusable, others think that his side b and aerials are amazing and will make him at least pretty good on top of his down-b. There's probably too little labbing and actually relevent matches to look at to call it yet.
-Inkling has many amazing options but lacks kill pressure, many seem to think they are very good but difficult to master.
-Pokemon trainer is probably way better, but Squirtle stands out to most top players as the standout among it's pokemon. Squirtle has a really good combo game and is hard to land hits on due to it's small hitbox. Whenever squirtle gets too beat up, you switch to charizard for increased durability, kill power, and recovery.
-Pikachu's new nair greatly improves his combo game, he's better than his smash 4 version but it's debatable by how much.
-Rage only activates at 120%, so it's not common you'll actually see it matter in most matchups unless you are a very heavy character (like bowser, DK, etc).
-Snake plays much like his brawl form, but is much less campy with the loss of his old Downsmash. He's got really good options to not let characters off stages and while his tilts aren't as good as in Brawl, they are still really good. His C4 is probably better than it's brawl version, and he's not necessarily among the best but is not lower than mid tier either.
-Almost everyone was happy that Stage hazards were toggleable and that there's probably 25+ legal stages in this game.
-dash-dancing varies in viability from character to character: inkling and littlemac have a dash dance very similar to melee, while bowser/charizard don’t really have it as an effective tool.