It depends on the variant. In a large board variant like XXL, the rook is easily the best. However, in smaller variants such as rubicon, the general is one of the best pieces in the game. The wildebeest usually comes in handy in specific positions, but is rarely better than the general, and very difficult to compare to the rook.
You are right, for example: a non-royal king is stronger is stronger than a rook on a 3x3 or 2x2 board but a rook is stronger than a non-royal king on a 8x8 board, but what about the rook and the general on a empty 8x8 board: which one is better?
on chess.com variants all of these 3 pieces mentioned on the title are worth 5 points, the question is: which one is better