Meh. It isn’t so much about WINNING Iowa as it is that you can demonstrate the ability to put together an effective ground game in a reasonably small state. A top-5 finish, especially anything with 10% or more, shows you’re someone to be reckoned with and helps with ground game and funding for later contests. A total bust in Iowa pretty much means you aren’t going anywhere - you can’t win the nomination there, but you can sure lose it.
New Hampshire is really the useless one - it’s basically a contest for the title of Chief Squish. South Carolina, on the other hand, generally crowns the main conservative contender.
So, in your opinion, all of what you say could ONLY be done for IOWA and such a small pandered-to electorate with nonstandard (compared to the rest of Red State America) straw poll histrionics? Meh from my POV.......
Four decades or so ago, they were actually fairly reliable bellweathers. Not anymore.