Personally, homestuck's ending was okay. But there are severe problems.
1. The post collide stretch was marked with a lack of dialogue. This ended up with shit...
2. ...being implied, instead of being statec outright.
Compare Undertale:
Asriel regains his form by absorbing souls from every single monster, and fights Frisk, who is explicitly pacifisting in this route. Frisk visibily pacifies Asriel by going through the rounds and empathizing with their souls, showing methodology and cause. Frisk's powers are explicitly explained because of determination, or a power only humans have. Determined humans could reject outcomes and restart at certain points in their lives. This power is stated to be innate.
After Asriel realizes his mistakes and the full weight of his actions, he restores all monsterkind via using his godlike powers, and the monsters are shown to be alive and well, and their main obstacle: the barrier, broken. They then leave the caves to appeal with the rest of humanity outside.
Only Asriel remains in the caves.
The only thing people have against this is that, that character remains in the caves by virtue of his actions and believe him to be unworthy of suffering that fate.
In homestuck's case, the leadup is basically humans standing on the final floor, the rings being dropped into the forge and quite possibly causing BS to wake up and fertilize Skaia, to grant them their final wish and restore the world that they had. In the meantime, Lord English is killed offscreen via an applied dose of cueball into his eightball face into the black hole.
We are not exactly told about the powers of the weapon (deus ex machina), except that it can undo Lord English, and for some reason, it grants John his power to retcon shit. Was the weapon active all along and LE's death at that point being guaranteed?
The other factor is Old!Calliope. Her existence also smells of deus ex machina, by virtue of her presence not entirely being explained. How did Calliope gain powers par Lord English, when, i'm sure I forgot, but she wasn't prototyped with a guardian, sprite, another player, an insidious calculating pair of glasses and a guaranteed immortality from everything? How is she able to create a black hole out of nowhere that is equally powerful to that of the green sun, when she isn't basically Lord English? Jade, being prototyped with a guardian, doesn't lose her powers and manages to resize the world back to normal, when the green sun is a constant in all universes?
There's a lot of information that could have been explained had calliope not been obscure as fuck and the story adapting a normal dialoguelog approach on act 7.