Back in the previous century (the 1980s), golfers used to do the Hi-Lo drill to get the long irons working. The idea was to mimic the smooth tempo of the short irons with the longs...
Hit 3 shots with a 9i, then 3 shots with a 4i
Hit 3 shots with an 8i, then 3 shots with a 3i
Hit 3 shots with a 7i, then 3 shots with a 2i
Also, the lofts have changed. My old MacGregor MTs had a 21* 2 iron; on my TM SLDRs, 21* is a 4i. (You can't compare exactly, because SLDR clubhead is a lot more efficient for launch than the MTs). Stronger iron lofts have helped make the hybrids popular, since the 3i has such low loft these days.
Club designer Tom Wishon suggests the 24/38 rule: The average golfer can't hit an iron that has less than 24* loft and a shaft longer than 38 inches.
If you must hit long irons, consider getting the shafts softstepped: This involves putting a shaft tip-trimmed for 2i into a 3i, then 3i into 4i (then butt-trim to length). This increases the length of the flexible portion of the shaft, softening it by 1/3 a flex and helping out with the launch. An old-time clubmaker told me that back in the 1980s, he would always softstep the 2i and 3i for customers without telling them.
If you get flighted shafts, you get a similar effect. For flighted shafts, the long irons are softstepped... PLUS, the short irons hardstepped (to prevent ballooning of shots).
This is the dynamic portion of the swing that you seem to be gleaming over. Most people can pose (like for a picture) to look like a pro at setup or at finish. It's the getting from the setup to the finish in an efficient manner that gets the ball moving quickly that's hard.
My round was in one work "Yuck." 1 birdie, bunch of pars, a few bogeys, couple doubles and a triple and quit on the 14th after a drive that ended up 20 yards from the pin in the middle of the fairway on a 272 yard par 4 because it hit a tree and bounced back in.
I seem to focus better when people are watching me, and if I really need to make a decent shot.
If on my own, I'm totally careless. Double yuck.