I would argue that a lot of what you are suggesting there is very marginal in some areas of the US. 223 is not legal in most northern states because it is insufficient. 243W @80gr and 300BLK @110gr are very low sectional density bullets (0.19, 0.165) SD <0.21 should be a minimum and <0.25 better.
I agree that shot placement is more important and probablly millions of deer have been killed with these caliber/bullet combos. But there will be situations that those combos will be insufficient, but 243W (or 6ARC) @105gr would not be.
SD <0.25
.243 - <103gr
.257 - <116gr
.264 - <122gr
.277 - <134gr
.284 - <141gr
.308 - <166gr
I'll stick my neck out here... I'd rather see a kid use 22 ARC @88gr than 300BLK @ 110gr.
If you would have read my early post, I did mention if 22 cals are legal in your area. I was referencing the ops request for low recoil loads for a kid, and as I stated above, there are numerous such loads available and was only giving a couple to few.
Over the decades, I and many others have killed numerous deer sized game with various 22 cals, 6mm reduced loads, 6 & 7mm TCU handgun loads, 308 reduced loads, 300BLK loads, pistol calibers, etc, etc, so they are very sufficient for the task.
If one doesn't have any or much real field experience with these calibers and loads, they may think these loads are insufficient, but within their range with proper bullet selection, they work. Kids typically keeping their shots much shorter than olders.
All of the above are as or far more effective than a 45-50 cal round ball and some conicals in a muzzle loader, but most people have no issue accepting those as viable deer killers.
Edit: Don't get all caught up in "numbers" of SD and such, for I and many have seen far too many 30 cal Barnes 110-120's go completely through deer and hogs from 300BLK and others. Similar with the 85 Speer BTSP and 80gr TTSX from various 6mm rounds, and many of the 22 cals designed for larger game. I would say 80% of the broadside deer hits I have made with my 22 cals, they were complete pass throughs with plenty of tissue damage. Many times very similar to 6mm.