I think the single best step to curb presidential power would be to abolish the veto power.
The veto effectively makes the President the most powerful person in the legislative branch (despite not even being
in the legislative branch) and also makes it virtually impossible for congress to take back any power it has ceded to the President. Congress passes a law saying the President can do something? Well, good luck taking it back! If Congress tries to do that, the President just vetoes it. And you can't get the required supermajority of houses to override it because you'd need both parties to get on board to hit the required 2/3, and why would the party of the current President want to curb their own President's power?
Abolishing the veto would allow congress to claw back its power and help government work better by removing gridlock.
This article (by someone else) puts forward what seems to me to be a pretty strong argument for doing it, making the points I noted above:
Some Constitutional Amendments #1
decivitate.substack.com
Technically, their suggestion is not to remove the veto entirely, but simply require a simple majority to override it, turning the veto into more of a note of caution from the President than the power it has not. In either case (a total removal of a dramatic weakening) it gets rid of the President's extreme power over the legislature.
Of course, passing an amendment is excruciatingly difficult which means this would probably not happen, but as this shift wouldn't inherently benefit either party over the other (I suppose it would weaken the party of whoever is currently the President, but you could just have the Amendment only take effect at the start of the next presidential term), I could possibly see it happening.