I don't think he is that poor. Good on crosses and bosses his penalty area quite well, not the greatest shot stopper but not as bad as some make out.
It's another injury for the Palace so can't be all bad news.
Just a rumour but he is out injured and Palace currently only have a twenty year old to fill in.
https://www.101greatgoals.com/news/crystal-palace-wayne-hennessey-spurs/