Is there a liberal alive today capable of engaging in the type of civil debate that would be necessary to address such a huge question? The handful I can think of lean libertarian over modern Democrat -- and so I doubt today's liberals would even let these types represent them in a public debate. What I see instead in a bunch of bullies who have no desire to listen to anyone except those already inside their own echo chamber.
The current gun control proponents do not care what we think. They do not want to talk to us about it. They simply want to cram it down our throats with zero discussion. This is one reason the Constitution was written in the manner it was. So that individual citizens would not be at the mercy of mob rule. And so that our core rights could never be denied at the whim of a simple democratic majority. The majority (or mob) cannot make the rest of us follow a state religion just like they cannot subject us to cruel and unusual punishment, or deny us free speech or the ability to peacefully assemble. The right to bear arms falls into this category, it is a civil right. A mob cant take it away.
IMO, amending the Constitution is a hill to high for them to ever climb. At least in any of our lifetimes. Based on what Ive seen of the folks currently throwing this idea around, they do not have any idea what is actually required to make it happen. We are never going to be able to address this issue properly until the other side comes to this realization.
There are probably individual liberals out there who are capable of debating the issue and seeking a consensus - whether it requires changing the Constitution or not. However, the liberal base of the modern Democratic Party is not. They pretty much want to shove their agenda down everyone's throat. They're very emboldened, even as they've been defeated at the polls.
Nevertheless, if you don't believe in the supremacy of the written law (as liberals largely do not), then going through the trouble of amending the Constitution is a bit of a needless headache. Why make the political compromises and fight the battles needed to amend the Constitution when 5 guys is black robes will just force your will without regard to the written law and with no compromise or effort?