The SCOTUS determines if the laws passed by the legislative branch of the government are constitutional. If congress passes a law they deem constitutional (according to you) then it doesn’t have to go before the SCOTUS. Like Obamacare then. Congress passed it so according to you it’s constitutional.
That's not what I'm saying. I'm saying that all three branches have a responsibility to ensure that laws are constitutional. The courts determine whether laws are constitutional, of course, but so does (or rather, so should) Congress and the President. Three co-equal branches of government is the basis for the checks and balances that make our Constitution work.