To stick with your analogy, I was trying to express that any trickle that makes it downstream is assured of being stemmed by a partisan SCOTUS that is tantamount to a dam.

I hear you. But I worry that progressives sometimes misdiagnose what the real problem is. In this case, I really don't think the problem is - or ever has been - the courts' (or the Court's) treatment of the 2A. Or at most, that such has been downstream of the real issue.

Instead, it's that the nearly overwhelming legislative consensus in this country has been that as a general matter law-abiding adult citizens should be legally allowed to buy nearly any type of firearm (other than automatic weapons) they want. Even after three or four decades of intense activism pushing for gun control (at least since the Reagan shooting), and even after all the mass shootings and school shootings, even the Bluest, most progressive states still pretty much let any adult citizen with a clean record buy nearly any type of firearm in whatever amount they want. Even before Heller and McDonald came down, no state was seriously trying to broadly limit access to firearms.

That stuff matters. When you have such a broad recognition that people should be allowed to have guns, it makes it much easier for the courts to interpret that ability as being protected by Constitutional language. It's part of what happened with Obergefell, actually - once states stopped differentiating between gay and straight people in disparate areas like adoption and inheritance rights and other matters, it became harder for the Court to argue that marital rights weren't covered within the broad liberty language of the 14th Amendment. I think similarly, because every state legislature generally recognized that people should be allowed to buy guns if they want, it became very easy for the Court to rationalize striking down the all-but-bans of the handful of cities that didn't - because they were targeting a legal entitlement that every other level of government was pretty uniform in saying ought to be available to people.

So-called "common sense" gun laws are both popular and largely irrelevant to the problem. Gun laws that would be very relevant to the problem (like those of DC or NYC) are sufficiently unpopular that they can never, ever be adopted in any state. And that's why we're where we are.