Yes he can and he does. Asriel most definitely gets saved by Frisk in the game. We just don't see it happen because the ending is meant to make us so emotional that we write fanfics and draw comics about the ending that truly happens. There wasn't any message of not being able to save everyone and the only possible outcome for the storyline is for Frisk to keep resetting until he finds a way to save Asriel because that's the goal he's set out to do since the final boss battle. Frisk is the kind of the person who would never be able to live happily knowing an innocent was stuck suffering the worst fate imaginable. He is the kind of person who would be unable to move on and just enjoy his life because he'll constantly be thinking about Asriel and how he's miserable.



Frisk definitely goes back in time and keeps searching for a way to save Asriel. It doesn't matter how many times it takes but he will not stop until he finds a way to do it even giving up his own soul in the process to do it.