The reason there is no cohesion is because there is very little similarity between Melee and its successors and are related in name only. The differences are so stark in the forms of gameplay encouraged that you might as well be talking about the cohesion between Smash fans and SF fans.
The point is that there doesn't need to be harmony between Melee fans and Sm4sh fans. Melee fans don't further the goals of Sm4sh fans and Sm4sh fans certainly don't share Melee fans' wishes.
We really need to stop harping on the idea of unity between Melee and Sm4sh fans. We don't need to support each other, we're not on the same team. We can be civil but the differences between us are written into our DNA. Honestly, we're ideological enemies (generally speaking) as the two groups in almost all cases would love to see the ideals of the other group completely vanquished from gaming. Melee players are generally disgusted with the entitled, dismissive, immature, petulant attitude of Sm4sh players. Sm4shers feel the same way about the tired neck beards who can’t move on from a 15 year old game and embrace change.
Seriously it’s not good for either community to pretend we’re all of the same mind and same want. We’re not.
This isn’t a broken community. It’s two communities.
I fail to see how co-existing in not just a "civil" way but a harmonious way is somehow harmful to either community.
The players who prefer one game over the other are entitled to their preferences, that doesn't mean they have to go out of their way to put hair in the other's soup. The idea that these people are "enemies" is absurd. Supporting both games doesn't mean you have to play or even like both, thats not what support is. I'm sure some people here have loved ones that they don't get along with or that make divisive live choices but they support them regardless. Fostering growth and positivity is all that support really is. The games will naturally lean on each other whether the few who disagree want them to or not anyway. Brawl brought many new players to the Melee scene, and Melee vets that were willing brought Brawl years of experience and insight. Thats all going to happen again, it's just a matter of how its handled thats the issue.
You are a little off base by saying the games are to different to compare, that you may as well compare Smash to Street fighter, because that community already faced its own devil and for the most part moved past it. I keep having to say it, and I wonder if its just because I'm old (ugh) or people just didnt pay attention, but there was a lot of controversy over SF4. There were those in the community who thought it was dumbing down the game to much from SF3, that it was to defensive. SF3 and SF4 may share the same fundamentals, much like Melee and 4, but on that same token they are vastly different in their execution of how things play out. SF3 is without question a more combo heavy and technical game than SF4, but at the end of it all the community moved on from such childish things such as flamebaiting, trolling, and just general active negativity toward one another(again, for the most part). SF4 had its place, and those who didn't care for it understood that it didnt suddenly delete their game from existance, something thats especially true for Melee.
Smashers can learn a thing or two from other fighter communities with differing games in the same franchise.