250 grains is just about perfect for any NA game animal; I completely agree. But the question that arises from that assumption is: Why not use a .338-'06 to do the same job? "Because I already have a .358 Whelen that I like and I enjoy shooting it" is a completely reasonable answer, and tons of calibers exist for that reason. My point was that a .338 will struggle to fit a bullet over 250 grains whereas a 9.3 or .358 can fit a 300.
I almost exclusively shoot handloads, with the exceptions being 9mm, 5.56 and .22 LR practice ammo that only needs to go cycle the action, make a hole in the paper or ding on steel and tell me if I was aiming well. For everything else, I just need components available and I'm happy. If the bullet makers can make a variety AND sufficient quantity of high quality bullets in every 0.001" increment from .177 to .510, then more power to us all. We can have grand keyboard battles over the merits of the 248 grain .356 vs the 250 grain .358 and derive that much more enjoyment from the hobby. But when components get scarce and even very popoular components aren't available, that's when I wonder if a winnowing of calibers (not so much cases, since being reusable gives each case manufactured 3-10x the relative utility of each bullet manufactured) might not be best. .257 vs .264 and .243, .277 vs .284, .338 vs .323, .358 vs .356 and .366, .375 vs ..404, .416 vs et c.
I think that obsoleting guns and calibers that folks have put money and more importantly effort into is bad for everyone, and my favorite solution is that at least SOME runs continue in all calibers. I have looked at what would go into actually making cup and core bullets, and if worse came to worst, Casting copper cylinders and then milling them into bullets would be doable if not time-efficient.
This is pretty off topic already, I'm just trying to explain my underlying thinking. To be clear, I don't want and hopefully won't have a dog in this fight, but there was a time not long ago when this very issue arose for all of us and sadly I think that the possibility of shortages arising again now plays a role is cartridge discussions.