Having watched PMQ's for donkey's years, it's obvious that it isn't about answering questions ( after all, it would be easy enough to find out the answers, outside the chamber.)It's about ( for the PM) getting the confidence of his/ her own party, and for the Leader of the Opposition, about getting the same confidence from his/her own side.So of course there is grandstanding, showboating etc, as that is all part of it.
PMQ's is just a tiny part of politics in Westminster, the serious and important stuff goes on elsewhere.All this talk of bullying and nastyness is childish, as all the MP's understand what is going on, and if a leader can't deal with it they probably should not be leader( in Corbyn's case he has already lost the confidence if the majority of his own side anyway.)