Knowing an opening isn't the same as memorising moves. Knowing the opening is more about understanding the position, it's strength and weaknesses, the immediate tactics available, and the natural flow of pieces towards their strategical aims.
Yes, tactical lines do require more knowledge of concrete lines, because they are complicated to work out over the board. But at that point the memorisation should be a "summary shortcut" of your understanding or assessment of the position.
If it were about memorisation, what happens when both players reach the end of their memorised lines? If it's not mate, or one player being substantially better off (in which case, why did the other player memorise that line too), how do you proceed from there?
And that's where knowing an opening comes to the fore, the important part of the opening isn't the moves themselves, but how the game opens up to the middle-game. Understanding the types and structure of the middle-game that's derived from the opening is a far more valuable investment of time. For instance, knowing how to play with and against an isolated d-pawn - a significant number of opening variations lead to these kind of structures. Hedgehog structures, static double-pawn structures, backward pawns, outposts on an open file.
Knowing how to play a position is long term more valuable than memorising a routine of moves. Understanding over rote-repetition.
Granted, some positions are predominantly tactical, and those you need to calculate - either at the board, or before hand. Memorisation is a poor substitute for actual experience.
One of my proudest over-the-board achievements was understanding how to exploit the positional drawbacks of the Black side of a Stonewall Dutch. And beating a player 600-700 Elo stronger than me because I understood the White knight manoeuvre from f3-e5-d3, before exposing Black's backward e6-pawn by opening the centre with the f3 + e4 pawn advances. I spent a week trying to understand one model game of that opening, white's plan was logical, and the strategic aim of exposing the backward e6 pawn easy to understand and attempt.
Yes, tactical lines do require more knowledge of concrete lines, because they are complicated to work out over the board. But at that point the memorisation should be a "summary shortcut" of your understanding or assessment of the position.
If it were about memorisation, what happens when both players reach the end of their memorised lines? If it's not mate, or one player being substantially better off (in which case, why did the other player memorise that line too), how do you proceed from there?
And that's where knowing an opening comes to the fore, the important part of the opening isn't the moves themselves, but how the game opens up to the middle-game. Understanding the types and structure of the middle-game that's derived from the opening is a far more valuable investment of time. For instance, knowing how to play with and against an isolated d-pawn - a significant number of opening variations lead to these kind of structures. Hedgehog structures, static double-pawn structures, backward pawns, outposts on an open file.
Knowing how to play a position is long term more valuable than memorising a routine of moves. Understanding over rote-repetition.
Granted, some positions are predominantly tactical, and those you need to calculate - either at the board, or before hand. Memorisation is a poor substitute for actual experience.
One of my proudest over-the-board achievements was understanding how to exploit the positional drawbacks of the Black side of a Stonewall Dutch. And beating a player 600-700 Elo stronger than me because I understood the White knight manoeuvre from f3-e5-d3, before exposing Black's backward e6-pawn by opening the centre with the f3 + e4 pawn advances. I spent a week trying to understand one model game of that opening, white's plan was logical, and the strategic aim of exposing the backward e6 pawn easy to understand and attempt.