Naseem is not unfit. He is fit. That pic circulating is him breathing hard, gasping for air.
I don't think there are massively unfit players in the Test side. It's a skills/talent/endurance issue.
You can't come back after a year and look to bowl 20 -30 overs in an innings with consistent speed and accuracy.
Shaheen has the opposite issue in terms of playing all kinds of useless leagues and all formats when he should be taking time off and working on his bowling.
They are just not capable of executing the level of skill required for that long.
The other 2 bowlers don't have the ceiling of these 2 bowlers and while they were more accurate , they won't get much better no matter what.