I don't know if the recruiting to a lesser standard is necessarily a response to the lack of CAR recipients. When was the last time a person had to skin the cat on a pull-up bar for combat. I think some of the reduced need for fitness arose from the specificity of needs of the soldier and some elements of fitness are simply unnecessary for any era.
The need to carry more and more technology is a driving force for improving strength in the modern warrior in my opinion. Wrestling a guy to the ground for flex cuffs is different when wearing 70lb of kit than it was 80 years ago carrying around a few Garand clips. Armor, a basic load, NVG, radio, blow-out kit, tools, etc. weighs a guy down. Knees and back are a vulnerable point for todays military.
The composition of the military has more desk jockeys as a percentage today than 80 years ago but we still have a lot of basic infantry across the services and a higher demand for SOF than ever before. I think it's for the better to focus on the two ends of the spectrum too because long range doesn't enable the same level of intelligence gathering, reduced collateral damage, cost-to-benefit, logistics support, etc.