Maharaj bowls in the worst spin conditions in the world so he can probably be excused a bit.
Rabada is still only 23-24.
RE Maharaj, that's true but up until about 15 months ago he looked like he could take wickets in most if not all conditions, and like many spinners looked particularly dangerous on turners. Since then he's just been completely ineffective in general - even in subcontinental conditions and Cape Town/Port Elizabeth (which traditionally favour spinners more than other SA grounds) he's paid dearly for his wickets.
Rabada I agree with.
If I was SA I would risk losing some tests for long term gain.
Prepare some green flyers, keep competitive that way, while giving the next crop of batsmen a very tough initiation into test cricket. If they rotate through 8-9 batsmen to try and find a combination, and the ones that stand out have crafted their art on tough pitches, it might help them build for another tilt in 3-4 years
At Test level yes, at franchise level I'd have more varied wickets so the domestic batsmen can learn to bat in variable conditions. From memory, CA went down the 'green flyer' track at state level some time back and it didn't really work because it made quicks look more dangerous than they actually were while not improving the techniques of the domestic batsmen much. Alternating between Kookaburra and Duke balls has worked reasonably well from what I understand so they can try that.