You are right that Charges patronales and charges sociales are not really "taxes" , in fact some politicians (LFI and EELV come to mind) insist on calling it "socialized portion of the employee salary", which is a better description.

However doing this would cause a mind shift where the employees would realize how large a fraction of their compensation package is in fact retained by the government either in the form of taxes or in the form of charges. A positive outcome of this is that it would force this realization, since so many people think healthcare/education/pension are free...

Another aspect to this is that different corporations have been allowed to charge these Charges patronales and charges sociales at different rates (for instance nurses pay 14% for retirement, whereas the rest of the population pays 28%...). Worse an entire half of the workforce, namely all the civil servants, have no Charges patronales and charges sociales at all (in other words, the French state is a special employer that gets away with not paying for these, paying for the actual pensions out of its general budget rather than its stowed-away-for-later funds.... and when the French state goes bankrupt, it just needs to raise more taxes on the private sector employees to make payroll on its pensions!).