Your main point is valid, but I'd argue it's less the power of the President and more the two-party system and the weakness of Congress that is the root of many American governance problems. Executive power has grown in the vacuum of Congressional impotence.

As far as reforms, we need more to be sure, but there's at least the 22nd Amendment, formalizing the two-term tradition that Washington initiated and FDR abrogated into a hard limit, that means Trump can't legally keep power past 2028.