I understand where you're coming from, however this exact type of logic of separation of powers has only ever been invoked when trying to protect inhumane policies in the US.
For example, Colorado and other states have legalized weed. They don't need to wax poetic about separation of powers etc to defend their position, because everyone understands that this is exactly what the Federal system was designed for. To allow states to augment their economies and taxation systems as they see fit (going back to colonial era reasoning).
Throughout US history the most vocal proponents of states rights have been those who attempt to limit personal liberties. They first use the constitution as a jumping board, arguing that "it's not explicitly stated in the constitution!" because the constitution is limited and vague (The founding fathers intentionally kicked the can down the road for racial issues). Technically, the regressives are right here, but they are hiding behind legalism to protect their abhorrent viewpoints.
"If it's so popular then just vote on it then!"
Unfortunately it's not so simple. At the Federal level, a filibuster proof majority is required in the Senate (non-proportional) as well as full control of all three branches of government (president and congress are also non-proportional, although in a different way). So it's incredibly difficult to pass overwhelmingly popular legislature/amendments in the US. Which is precisely why we have seen most of our civil rights gains over the last 50 years be accomplished through the court system. At the state level, there is no filibuster (mostly) and so there is no mechanism for a minority to halt legislation at the state level.
This kind of game has been played out for the last 200 years. Yes rules are important, but the reactionaries in US history have typically "meta-gamed" the flaws in our system that were overlooked by the founding fathers in order to preserve horrendous practices. That's not to say that there is no benefit to our checks and balances, but when it comes to things like civil rights, gay marriage, and abortion, the opposing side is mostly meta-gaming and exploiting checks and balances negatively.
To sum up, corruption in the third world occurs by circumventing the laws. Corruption in the US occurs when you put someone in a position of power to interpret the laws the way you want them to. If you need sources, I can provide.
> No other developed country has approached the abortion issue by saying "pfft the rules don't matter."
The Roe decision was not made on "rules don't matter" it was an extension of the due process clause in the 14th amendment. The overturning of it was made on interpretations of common law going back to the 14th century, the main point of argument being that there was "no innate protection of abortion as a fundamental right".