A while ago I would have agreed on the fast twist, but recently started to work on a fast twist 25-06 and realized, there is a hard limit for bullet rpm depending on materials. This means you can’t keep fast twist and go faster velocity without limits. Start running around 4000fps and twist can’t get much faster than 1/8 for lead/copper. Pretty sure you can plot a limit of twist vs rpm by bullet type. This in a roundabout way gives you a maximum length per caliber, which can translate to max BC per caliber. While I have not done all the math, I think we are getting close to the limit of our current materials. There might be a few calibers that have not been optimized, 35+, but 30 cal and smaller sure have.
The artificial constrains of short and long action and 3 bolt faces really limits development of new cases. Although I am not sure you could do a lot better with a clean slate.