Gator, you just nailed it right on the head.
In modern times, with the enourmous popularity of CPR, mortality on released fish kills far more large fish than keeping them does, according to numerous studies and surveys.
So strictly statistically speaking, making it CPR, while possibly adding more small or medium size fish, would not increase the numbers of large fish. The only way you could do that is to simply close it to fishing.
I personally rarely keep fish, but I admit I do KILL fish. Stresses of being caught and handled are very high, especially on bigger fish. This is why I never, ever, talk bad about anyone who does choose to keep any legal fish. The fact that I release does not guarantee the survival of that fish, and in fact quite the opposite, it does almost guarantee I at least shortened the lifespan of that fish.
My personal opinion is that conversation efforts are much better suited to focusing on eliminating pollution and increasing water quality in general (i.e. less waterside development, dumping, etc.), eliminating invasive species, and other long-term or permanent-term efforts like that.
The thing is, an individual fish is not permanent. It will die, of something. And in the old Miss, they die pretty young (relative to northern lakes). For those reasons, I always view CPR as more of a temporary solution.
Note that I’m speaking of walleyes/saugers here, and my thoughts also apply to all our species of bass and sunfish. My beliefs are different for other species, including Northern, Musky, Sturgeon, etc.