The big problem is that neither party in power wants to change the system. After all, they're beneficiaries and creators of the status quo. This could only change if somehow a new party emerged, which is quite unlikely.

Right, that's why, despite its being about as close to a dull, settled fact in policy-wonk and poli-sci circles as anything is, that the US system sucks in about a dozen important ways that other modern democratic systems do not, we cannot fix it.

The system is broken in ways that prevent fixing that very brokenness. We know exactly what's wrong, but can't do anything about it. You'd have to get a whole bunch of people whose personal power is tied up with the status quo, to, all at the same time, vote to weaken that power and the power of the organizations that put them where they are. Or you'd have to get at least some of the states that benefit from the brokenness to agree to weaken themselves. Neither is likely to ever happen—short of some very risky and probably-bad-rather-than-good developments that are more likely to end in authoritarianism than an improved democracy.

Well theoretically you could, it's just that the big states would have to offer up an amazing deal to entice the smaller states to agree to call a constitutional convention.

The supermajority of the electorate in the smaller states might be willing to exchange future political influence for sufficient wealth or some other compensation.