In case you didn't know, the true pacifist ending isn't available on your first playthrough anyway. You must complete at minimum one neutral ending first.
Undertale became massively popular so now everyone knows everything about it, but the game is designed for players to come into it blind & with the expectation that it'll be a normal JRPG. You're meant to kill monsters, be surprised that they stay dead, finish the game to learn why, and then be told to avoid combat as a new game+ challenge run. You're not supposed to know the gimmick beforehand and start the game with the challenge run.
There's something to be said about how subversive things lose their appeal when they become so popular that they lose their subversiveness. But yeah, go do some grinding because you're probably level 1 and have garbage equipment.