I don't see what he adds. He isn't the only player to be poor lately, but even when players are poor it's usually quite obvious what they're good at. When Martial is playing badly and not beating his man and not getting the shot away, you can tell that when he is playing well he'd be beating his man and getting his shot away. When Carrick's passing range is misfiring you can tell that when he regains form his passing will be back to its best. And so on.
With Lingard it's genuinely hard to tell, even if he does end up having a good game, what it is he'd actually end up doing. He's just....there. Might as well be that soggy tied-up bag of lettuce you inexplicably get sent whenever you order take-away from any variety of Asian-based food restaurants. You see it there, but you never know what the point of it is. Yet every time without fail it turns up.