He's often left to defend the whole right wing alone, they 2vs1 him constantly and sometimes you can even see him in 3vs1 situations with the CM, it doesn's Pique going out of his spot to cover a huge gap left by Busquets or to commit to an awful tackle doesn't make things easier for him either.
Not saying he's not to blame, but you can't judge a defender on a team that basically doesn't know how to defend and has 0 defensive workrate and solidarity, people are saying that Lenglet had a nightmare today because he's in the photo of every goal, but at least he's trying to be the firefighter solving fires everywhere, someone like Busquets doesn't show up because he basically doesn't even try anymore.