I worked for all 3. Started with Caremark and CVS bought them. To be honest CVS didn't understand the PBM business and just got rid of the top people and Caremark is ok but no longer great. Caremark did move up in the ranks with Maintance Choice as it helped CVS and some of their smart people began advancing.
Ended up at part of Aetna in an area away from the main business. Aetna is all politics with 'can you sell insurance'. You could tell them a mile away as they lived to talk about top people by first name.
Trouble is the worst possible leader for the combined company was chosen in Karen. Top it off she began her reign as Covid hit and it was good for healthcare companies. She decided it was due to her brilliance.
Karen is politician who needs her ego polished constantly. So focus was on a book, being called 'the most _____ woman' in whatever magazine she was interviewed in and being the queen of DEI. Pay attention to the business was not her thing. The phrase 'Nero fiddled while Rome burned'. Karen took a company worth $76 Billion after the merger and her purchases spent $88 billion to end up with a $78 billion dollar company. Karen could have burned that money and sold the ashes for more that she got back.