You would have about the same or less. Maybe UNH gets you a couple extra percentage points per year, but that's because they have an enormous healthcare provider business instead of just being an insurer. But it's still nowhere near a positive risk adjusted return when comparing to a relatively risk-less investment in SP500.

https://dqydj.com/sp-500-return-calculator/

https://dqydj.com/stock-return-calculator/

Since Jan 1, 2010, 18% for UNH, 15% for MOH/CNC, 14% for CI/ELV/HUM/SP500, 8.5% for CVS.

Also, these businesses are competing to sell a completely fungible commodity good with tons of non profits like Kaiser Permanente, HCSC, Cambia, Independence Blue Cross, and many others. It makes no sense to expect those businesses to be able to earn any decent profit margin when their competition only needs 0%.