With a 200 grain premium bullet the .300 WM is at its best.   I miss the 200 grain Swift A-Frame Remington used to load in its Safari Line of Factory ammunition.   Federal used to offer a 200 grain Nosler Partition in its premium load.   The reason I use a 300 WM instead of a 30-06 is that I can use a 200 grain bullet at about the same trajectory as the good old 30-06 does with 165 or 180.    I don't need the extra range, I like the extra punch of those heavy bullets within the same range.     I like heavy bullets.  I also keep my shots within 300 yards.   Thus the preference for heavy bullets.  My friends like to shoot further and choose lighter bullets.   Each to their own.
I am not as near the experienced hunter as many on this board.    My personal experience is that heavy for caliber bullets do a good job for what they are asked to do.   I may need to hunt closer than others with long range set ups, but 300 yards is within my range with my heavy bullets.
I'll likely go back to Africa for a plains game hunt with my .300 WM,  ( I really want a .375........Holland and Holland.)
Everyone have fun hunting.