I mean people should have unerstood by now that he has lost pace over the years. Its not unser his control to bowl fast. He is doing whatever he is capable of.
He is still not being able to have good grip on the seam and rotate the ball with seam facing leg slip for the right handers to have that natural in swing. You can see this in tdays match, all the wiket deliveries in slow motion shows his seam position scrambled. He had this problem in Asia Cup as well after which he was dropped. Hw returned in SA test series and had that problem rectified.
Also lately, he has not been bowling length or above length to allow the ball to swing. Today he looked threatening only because he bowled little full.
If you take a look at Amir's threatening spell all have one thing quite common, its those full pitched up deliveries that allow the ball to swing in, let it be the Asia Cup 2016 spell or CT 2017. He should have learned it by now after analysing and looking at his best performances again and again, but it hasn't happened. I also criticise the supporting staff for this, they should have helped him with that.
I always say to my opening bowlers students:
If you bowl length in your opening spell, it is the wastage of bew ball.
This should be a termed as a saying in cricket, actually. It is the hidden universal truth in cricket. People understand that for the ball to swing, one must bowl full, but they don't consider bowling length with the new ball as a WASTE of new ball, which actually it is. And you are committibg a Crime in cricket
If you look at why new zealand have been so successful to get wickets in first 10 overs, it is because both of their opening bowlers Southee(outswing)and Boult(inswing) bowl full pitched up delivers to let the ball swing. Look at any threatening opening spell in world cricket, you would see the bowls being pitched up...... Starc of 2015 world cup... anyone remembers his spell vs new zealand, also his other spells in 2015..... yes, thats what i am saying, boult's spell where also breath taking in 2015