Unlike with other forms of media though, the players of fighting games are experiencing the story as it unfolds, so poorly designed mechanics can not only lead to simple disappointment but also frustration and possibly community-wide disinterest in the game itself.
As an extreme example, the Touhou fighting game called Scarlet Weather Rhapsody had to patch an extremely poorly implemented come-back mechanic in order to fix it. Originally, supers could be done at the single push of a button while holding any direction. Therefore, it was too easy to option-select, or even just mash, on the super-button while blocking during situations where you’d either block or reversal. To exacerbate this even further, some supers were fairly safe or even unpunishable while still being incredibly powerful. They fixed this by making it so you could not be blocking before doing a super, and balanced the punishability and damage of some supers. But the point is that this was originally a bad idea that was made a bit less of a bad idea.
The key ingredient seems to be just how easy it is to rely on, contrast with how baitable/punishable it is by the opponent. The comeback is made more appealing when the underdog has to really work for a victory; hence this is why the Deus Ex Machina is not as appealing, there’s nothing attractive about a free win. It’s exciting when it seems like a player really deserved the win, but a letdown when it seems like the other player “got robbed” of a victory.
However, if a comeback mechanic is implemented around the idea that it not only has a very large risk-reward ratio (meaning, very high risk and balanced reward payout) but it’s also not particularly easy to pull off, then it’s not only justifiable when it happens but commendable when successful. That isn't to say it should be useless, but rather just keeping in mind that there needs to be room for skill from both players. It's skillful when an aggressor is able to bait out and punish an opponent's comeback-mechanic, but also skillful when an underdog can land a comeback-mechanic despite the low odds of actually being able to land it and the risk involved when failing to land it.
In my opinion, comeback-mechanics have the potential to be good and enjoyable. If you're not able to avoid getting hit by comeback-mechanics and you're getting owned up because of them then you need to step up your game, yet likewise if you're not able to land a comeback-mechanic and getting steamrolled because you continue to misuse them then you need to step up your game. However, the mechanic itself also needs to be implemented well for it to even be enjoyable in the first place.