Agreed bullet construction is important.
I know a Woman who uses a 243 and another who uses a 257 Roberts. Both take elk .
I found when I replaced my primary hunting rifle (7mm Rem Mag) with a 257 Roberts AI,two things happened. Shooting became far more comfortable. That translated to havng both my eyes open and watching the crosshairs rest on a spot on the ribs. I tended to shoot better. You don't need all that much horsepower to punch through ribs and make soup of the heart/lungs.
The other is a sense of limitation. With a lighter cartridge,I have it in my mind that I do not have to pull the trigger. If I have a marginal shot,I can wait.If that means the critter walks,at least I have no regrets.
That said, I also have a 30-06 or even a .375 Taylor available.
I believe in using "enough gun" and I don't support stunts with underpowered rifles at the animal's expense.
That said,I do not consider the 243,responsibly used,as "A stunt with an underpowered rifle"