Playing rock paper scissors is about predicting what the opponent will play next given a history of moves.
Prediction is the dual problem of compression. For example if the history of moves is "RRR", you can try to compress the strings "RRRR", "RRRP", and "RRRS". Clearly the first one ("four Rs") is more compressible than the other two, so it is most likely that the next move in the sequence is also an R.
However, there is no universal compression [1][2] so there is indeed no universal optimal RPS player.