IMHO, it is a sin to insist that we know better than God does. We do not know better than He does.
We are not God. We cannot see the purpose in pain, but He does. We see bits and pieces. He sees it all. If He says we should suffer, for whatever reason, then perhaps we should go along with it, if we are to be obedient.
Even His own Son, Jesus Christ, suffered for us, out of obedience. And we are all the better off for His Sacrifice.
Again, this is JMHO.
JMHO, too. Disagree. People of good will can disagree.