Well, to understand why Melee hates Brawl it's essentially how Halo fans feel about Reacn and 4. It's how Quake fans felt about Quake 4, it's how UT fans felt about UT3. If you treated games like a competitive sport, you would be pissed off that the work and effort you put in just suddenly meant nothing. Hell, it's how Quake and UT fans feel about every other shooter in general because they became easier and were no longer skill based arena shooters.
Let's be quite frank. In online competitive games, the vast majority of people get good in games specifically to be better than others. Essentially to pubstomp. That's common sense. If I spent countless hours into improving at a game, I expect that lesser skilled players should be absolutely destroyed at my whim. It's the same principle. You pay your dues and expect to be rewarded for paying your dues. Melee players were betrayed by Nintendo for profit. That's the bottomline. Just like every other online gaming series has done. Quake, UT, Halo etc.
When you work a job, you expect to be rewarded for spending the time and effort to do it. Melee players expect to be rewarded by being able to do long combos and pwn noobs.
Heck, just look at my gif. If I'm not able to pull off long combos like that and pwn, the game isn't worth playing or investing time into.