That's not true. The President individually has way too much power.
But if we assume you're right, then we don't need a President, because all the necessary decisions are made without him.
We have two congressional committees that write the laws and establish budgets with 435 members in one and 100 members in the other. The president's primary job is to oversee enforcement of the decisions of those two committees.
You know that he repeatedly goes against their decisions as he wishes.
But he also issues his executive orders which are purely his own decisions, sometimes contrary to what Congress wants.
Why should one person alone have any power to make policy decisions? Why should he even have veto power? Why not instead have a "committee" exercise that power?
The president can negotiate trade deals and treaties but they are not binding until approved by those committees.
Why should one person alone have that power? Why couldn't a "committee" negotiate the trade deals and treaties (to be submitted for approval)?
And you omitted the "commander-in-chief" role which permits him to in effect start up a war (including whether to launch a nuclear attack). Why shouldn't there be a "committee" to make those decisions instead of putting all that power into the hands of one person?