The main reason most Pendle players leave his team vulnerable on 4v5 is because they go to destroy buildables/collect shards deep inside enemies base (even when the enemy is pushing) .
These players think this is Pendles main role, which I highly disagree based on my playstyle with his character. In overgrowth, the miiddle and base turret is always helpful to destroy and keep control. In fact, I wish more ranged players focus down the enemies turret. However, spending time on getting to and destroying any other buildable as Pendles is just hurting your team. During that time, it is more beneficial for Pendles to support a push, take out the squishy or most vulnerable enemies.
Pendles is extremely difficult to play against skilled players that have 2 or more BB than can reveal him. Very few players can make him viable in those situations. I’m one of those few but I get headaches after 1-2 matches.