This.
People are so desperate for a left back that they're suggesting that anyone is better than Cuco Martina at this point which is simply not true.
Whether you rate him or not, the guy has spent his entire career plying his trade as a full back, which is why he's being utilised as one albeit on the opposite side he's used to. He's not being played there out of whimsy like many seem to be suggesting - he's a professional footballer playing under professional managers & coaches, they clearly see more than we do.
Obviously he isn't a long term answer in any way shape of form.... but to actually suggest that a 21 year old La Liga striker who hasn't even been given a game in ages 'wouldn't be any worse'? Haha, give over.