Please name other fighting games that implement comeback mechanics on a wide scale. Explain their use.
The only game that has this is Tekken, but it only takes effect at the very, very end of the game (last 5% of health). Tekken doesn't have multiple stocks. The impact is low. Often, you will be in a combo when you get to that last 5%, so don't even get the chance.
"Comeback mechanics" are detrimental to competitive games. Real competitive games either don't have them or they are very limited.
In a competitive game, the winning player should have an advantage that he can use to press his opponent. The losing player has to then take riskier options that will either get him back in the game or end the game very quickly. This leads to very interesting, and very quick, matches.
This is true of every major competitive game- Starcraft, Poker, Magic, and Chess all meet this design criteria.
The winning player in Chess, Poker (Texas Hold 'Em), Magic, and Starcraft exerts pressure on his opponent and brings the game to an end very quickly by forcing their opponent to make riskier and riskier decisions to try to get out of the situation. If the opposite was true, you'd see longer games with more inconsistency (the better player does not consistently win, because the loser is constantly given handouts to catch up, and the only thing that matters is who plays better at the very end of the game). If the better player cannot consistently win, the game is not considered competitive.
I don't think Rage is bad enough to make the game noncompetitive, but it certainly contributes negatively.
Listen, I'm going to try my best to write this nicely because I genuinely want to teach you. I feel sorry for you if you genuinely think this is how Melee and Brawl worked, because it sounds like you are genuinely ignorant of it and letting positive feelings on Smash 4 blind you on this.
The beautiful thing about Smash Bros is that there has always been no set combos. There's a flow. People could change where they go after they get hit through DI, and being able to adapt to make combos was a beautiful part of Melee.
Games flow like a debate. You appraise your opponent's capabilities, you know what he WANTS to do, you know how to stop him from doing it, but he knows how to stop you from stopping him, and elaborate guessing games happen. David Sirlin wrote an amazing book on how this works, mentally.
You know the best options in any situation, but your opponent knows too. Your vast game knowledge gives you the ability to judge the changing game to figure out the best thing to do in a given situation, and also to figure out what your opponent wants to do.
Making stuff like knockback become "fuzzy" (inconsistent) through the combination of VI and Rage is bad for the game. Because in Melee and Brawl, when you hit the percentage where I can kill you with an usmash, both players know it, and it creates depth- you have this new threat, and suddenly, your opponent has to change up his decision making process because he knows you really want an usmash and YOU know he's going to be making choices that avoid the usmash. So you use that to your advantage to land your other moves.
When you can't really know if your moves will kill your opponent, that mental interaction in the high level of play is weakened.