Former Aetna CEO Mark Bertolini told CNBC on Wednesday that the flaws in the Affordable Care Act can be fixed without totally getting rid of the law.”To tear … this very important program out now, in the midst of this pandemic and huge unemployment, would be huge mistake,” Bertolini said on “Squawk on the Street.”Bertolini’s comments came one day after the Supreme Court heard arguments in California v. Texas, the third time the constitutionality of the ACA, also known as Obamacare, has come before the nation’s high court. The law appears likely to survive yet again, after two conservative justices suggested the individual mandate provision could be struck down separately while the rest remains in place.President Donald Trump and Republicans in Congress have been frequent critics of Obamacare, pledging unsuccessfully for years to “repeal and replace” the signature health-care legislation championed by former President Barack Obama. It was signed into law in 2010.Bertolini, who served as Aetna’s chief executive before the health insurer was acquired by CVS in 2018, also has been critical of the Affordable Care Act. In 2017, he said Obamacare’s insurance exchanges were in a “death spiral,” according to The Washington Post. While he was at the helm, the company also fully left those ACA marketplaces for health coverage.President-elect Joe Biden, who served two terms as Obama’s vice president, has vowed to strengthen Obamacare by boosting the number of people who are eligible for insurance subsidies and adding a public option, which would let some Americans buy a government-run health insurance plan similar to Medicare or Medicaid.”My transition team will soon be starting its work to flesh out the details so that we can hit the ground running, tackling costs, increasing access, lowering the price of prescription drugs,” Biden said in a speech Tuesday.Bertolini has his own ideas on how to improve Obamacare. “I think the ACA can be fixed,” he said Wednesday. “I think we need to look at the option of reducing age eligibility by means testing for Medicare for people that are older and aren’t eligible for Medicaid.””I think if we had done that in the beginning, instead of the ACA, we could have gotten as much done, a lot cheaper, because the risk mechanisms and the administrative systems in both Medicare and Medicaid work very well,” he added.Medicare is primarily for people who are age 65 or older, along with some individuals who are younger and have disabilities. Medicaid is the health coverage program for low-income Americans, and Obamacare allowed states to expand eligibility for it. In total, more than 20 million Americans have obtained health insurance coverage due to the ACA.”I think taking the bill down now would a huge mistake,” Bertolini said. “I think we can fix it by getting the risk mechanisms aligned to both Medicaid and Medicare, changing the eligibility requirement on Medicare, which would give us Medicare for more versus ‘Medicare for All.'” Some progressives, such as Sen. Bernie Sanders, I-Vt., have proposed shifting to a single-payer health insurance in the U.S., calling it “Medicare for All.”The Supreme Court is expected to issue a decision on the latest Obamacare case in June.— CNBC’s Tucker Higgins and Berkeley Lovelace Jr. contributed to this report.