That's true. But a legislature cannot choose a method that undermines the intent of the Constitution. For example, a legislature can't decide to put its electoral votes up for sale to the highest bidder.
I don’t think their doing so would be unconstitutional, though it would no doubt be illegal by state and possibly federal law.
Look, it’s very simple. The Constitution unambiguously gives the power to determine how electors are chosen to state legislatures.
For us to decide that “intent of the Constitution” overrides this power, we have to give a Court the power to decide what the “intent of the Constitution” is.
Either we believe in the Constitution as written, and in states’ rights to do even stupid things, or we don’t. Personally I think federal courts have far too much power now. I oppose any expansion of it.