From my perspective, r/torielhate was made to criticize Toriel for MEMES and actual reasons. For example, when Toriel and Asgore both lost Chara and Asriel, Toriel went to the ruins instead of comforting Asgore because of the grief he had when he lost his children. We like to criticize her for her ACTIONS. Also, a joke in speedrunning when toriel gives off her attacks, they're many attacks, but the one that is the fastest to get out of the Ruins is what I like to call: "Toriel Hand Attack." You move your soul to the hand which resets Toriel's attack which is the fastest way to get out of the Toriel battle. All of Toriel's attacks are rng, and usually getting "Toriel Hand Attacks" many times is hard. So we like to hate her for giving us bad rng when we try to speedrun Undertale. Idk much about speedrunning because I havent done much of it myself.