Robertson looks like the weak spot for Liverpool, while I do agree that he had a better than expected season, the red card is a proof that he is not their strong side, and they need someone better there without a doubt, someone faster, someone quicker there. Aside from that, their defense is too far up, which is fine when they are 11vs11 but when they were missing a player, maybe they could have pulled the defense a bit back, attacking with 10 people do provide some risks, which we have seen in this game.
Although in this match Robertson's red card was his own fault for not being able to control the ball well but I don't consider him bad overall just because he made a mistake in this match.
He was indeed one of the reasons for the draw for Liverpool in this week's match but that doesn't mean he's bad overall because in my opinion for this season he still looks quite stable in terms of performance on the pitch even on several occasions he actually became one of the players who contributed enough in providing a move to help Liverpool's attack line in terms of initiation.
The problem of players for Liverpool at this time is actually quite complex because instead of thinking about Robertson now that a replacement must be found, it would be better for them to think about how to keep the players whose contracts are running out at this time especially that it is far more important than the problem for Robertson.