Azhar can't open anymore too old, he clearly struggles his reflexes are gone. And really openers are just there to blunt the ball allowing the middle order to score, opening is way tougher especially for our batsmen, even in domestic our best openers average just high 30s even though the best middle order batsmen average high 40s/50.
Azhar is better off using his experience to score big in the middle order. He's still probably one of our best middle order batsmen.
Really openers can be anyone as long as they can give a bit of a start, blunt the ball. We don't need them to score huge scores, and if our best openers can only achieve a mid 30 average is all then that'll have to do. I think we're searching for these excellent openers which aren't there in domestic, no one averages way above the rest as openers, and even better batting talent countries struggle to find proper openers, look how England struggled to find proper test openers since Cook (or even strauss) retired. It's tough.
What you could argue is constantly dropping/chopping and changing openers, you're not even going to get the best of those average openers. I would have just chosen Imam and Sami before, they opened together in the past working well with each other, young enough to develop and probably the ones with the most potential. And just play them consistently without fear of dropping them. No opening pair really has any experience playing with each other, we keep changing them, and the guys we bring in usually have no experience playing with each other in domestic either.