Our core system of government - which has done pretty well for 200+ years despite all the undermining Congress & the Executive branch have done - is still better than the rest. It has done so well because it's a system built on principles that are eternal, it was specifically not built for any given time, but rather for all time. The only problem we have, is we need to return to a constitutional system of government, not be an extraconstitutional system, where the government intentionally ignores its limitations when it feels like it. We need to be a Republic again, not a mob rule Democracy that eats itself alive as is occurring right now.
The biggest problem America has is a vastly overreaching government, and it's overreaching in every regard possible, from privacy to fiscal to military to general freedom.
The only people advocating for an end or change to the Constitution, are those interested in various forms of authoritarian rule. Their goal is always, one way or another, to give more power to some central authority, and to limit freedom of the individual.