Clueless as usual. Morris' value is in the incremental runs he scores(which is less valuable given the top order has already collapsed) and the wickets he takes(which is incremental over a fairly reasonable bowling attack, he's not going to get replaced by someone who bowls 4 overs for 40 runs). Given that Delhi's big problem has been solidity in the top order around which batsmen can play, it is certainly worth testing a solid top order batsman around whom they can make big scores and see what they lose in the form of bowling potency. The other question to answer is Morris vs Rabada/Cummins, the latter duo being strike bowlers perhaps ruling in their favour. This must be the logic Delhi went through and it is worth testing. It's not a game in which you pick the combination from the squad which gives the maximum aggregate batting average and the minimum aggregate bowling average for any 5 chosen bowlers. Not something I'd expect you to understand.
Shreyas Iyer is a fairly accomplished first class batsman. He has good technique. Pant has had one good season and the jury's out on technique. Iyer was called up to replace Kohli in the last test squad -- he is a much better prospect from what I have seen.