The overall hate has primarily spawned because there is a very, very, very long list of problems with the game.
People take statements akin to that as simply being upset about Brawl not being "Melee 2.0", but consider this. Do you believe people whined and complained from the fighting game community when Street Fighter IV was announced? No. They were overjoyed that they were getting a sequel to a game they loved. Do you think they had a problem when the game was released? After all, it is effectively a new game, and not a complete cut and paste of previous Street Fighter franchises. The answer is still no. They didn't do this because Capcom grew upon the winning formula Street Fighter had going for it as a franchise. They kept the familiar but gave it a couple new twists. They added new features and new characters without stripping it of mechanics and features. More importantly, they did this properly without bugs or glitches, and the balance was reasonable.
You can also apply this to basically any recent sequel to any of the fighting game franchise names. Marvel vs Capcom 3, King of Fighters, BlazBlue from Guity Gear, Mortal Kombat. You get the point.
Rather than becoming a brand new Smash game that added something new to the table we could all learn and share, Brawl became the equivalent someone that was blind folded, stripped naked, turned upside down and beaten to death, and after being robbed left out on the street to rot.
Yeah, people are pretty salty about that. I'm not saying this to try and contribute to the argument, but you need to look at this in fair terms. There's a reason these debates even happen in the first place.
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Look, I'm not familiar with Street Fighter or Capcom fighting games, just saying there.
And claiming Brawl is like the way you did was just stupid.
It was an over exaggeration.
Auto-ledge grabbing: OK, I see why this is an issue, some characters can grab on to it at odd times. I don't recall characters being able to grab a ledge when facing the opposite direction of the platform at least.
Speed change: If people would actually bother to try and adapt, they would probably enjoy the game. I admit, some characters had a bad change of speed, like in Melee, Capt. Falcon could be sprinting and jump a great distance in mid-sprint. This is no longer the case in Brawl, so I can see an issue there. Other than running and jumping physics,I don't see an issue. The change allows more concentration, so I don't see how players would have a hard time adapting to that.
Shield and dodging: I believe it is no longer possible to reflect using a shield in Brawl, I'd like for that mechanic to return in Smash 4. Same goes for the rest of the shielding mechanics. I don't think it's huge issue though.
The air dodge is more understandable, you'll have to be more careful and tatical with it. I believe Nintendo made this change, to make things easier, mainly for non-competitive players.
There aren't any other mechanices or features I can think of that are an issue, I don't know absolutely everything about advanced tatics or the competitve Smash.