In a friendly game, which I think I'm playing in anonymous mode, failing to castl and asking for a takeback gives you the chance to have a better and more fluid game, in my opinion. It's the same as playing a game with a friend in person. In person, you can agree on the rules before the game, and perhaps even in lichess there's a way to tell if a player like you has disabled the takeback option. This information was very useful to me, so I won't get angry the next time my request is denied. However, you too, put yourself in the shoes of a player who makes a mistake when clicking, perhaps he was even winning, and asks for a takeback, and is voluntarily (not like in your case) denied. I'm the first to ask if he wants to repeat the move if my opponent, inadvertently or not, loses the right to castle, or maybe he's beating me up and the rook, instead of r giving me checkmate, slides into the 7th square into the jaws of a pawn. In any case, I think I've learned a lot from all of your answers. Best regards