There is no legal mechanism left that could correct course at this point. You would need to have a constitutional amendment to drastically reshape government and that's DOA. All that's left is snow decline and eventual dissolution
While there is a legal process for amending the Constitution which, as you note, is likely intractable in the status quo conditions, Constitutional change—whether peaceful (even if there is the implicit consequence of force if compromise is not reached) or not—historically and globally is often an extralegal process that is retrospectively legalized, rather than a legal process under pre-existing rules.
Now, an Art V convention could be seized on as an opportunity for organizing extralegal change, but then Art V process obviously isn’t necessary precondition for that, just a potential opportunity.