The President cannot spend a single dime without it having gotten through Congress. Blame it on “mandatory programs”, “baseline budgeting” or agreed budget deals, the fact remains that Congress has the power of the purse. But this is a power that the GOPe is afraid to use for political reasons and/or does not want to because they actually agree with the spending.
What is intolerable is the "whipped cur" variety of Republican, who either through cowardice, an inferiority complex, or actual perfidy, is unwilling to engage a President who refuses any compromise on his agenda, lest such Republicans get blamed for a shutdown, directly attributable to anyone with a mind to reason, to the intransigence of the President.