I should maybe amplify my answer a little. Please bear in mind that I'm not a lawyer, this is not legal advice, etc., etc.
Parzick is kind of complicated in its implications. The court in Parzick did not rule out the possibility that a room in your house could meet the standards of Mass.'s safe-storage laws. It specifically found that Parzick's setup did not meet the requirements of the law. The lock on Parzick's bedroom door was a "privacy" lock that could be defeated easily by a small child with a paper clip or small screwdriver and had a pushbutton on the inside. I think most of us would agree that that doesn't pass any kind of reasonable person's "laugh test" for security, and it didn't fool the court either. So they ruled that because the lock was so laughably and obviously insecure, Parzick had violated the law. The court did not say that a locked room of your home couldn't ever meet the safe-storage requirements.
What's the *minimum* level of security a room in your home would have to have in order to be considered a "secure container"? Consider, for instance, at the other end of the spectrum, someone with a particularly large and/or valuable collection who has a "gun room" constructed like a bank vault in his home, with concrete walls, a steel-plate door, and a suitably strong and tamper-resistant locking mechanism. I think if I had such a setup I would be able to sleep at night believing that I was in compliance with the law.
What if Parzick had gone up just one level and, instead of that laughable privacy "lock", had used, instead, a key-in-knob lockset that had an honest-to-goodness key lock in it? Your guess is as good as mine which way the court might have ruled. Honestly most rooms in most houses are still laughably insecure. Key-in-knob locks are easy to defeat by brute force or by picking. Hollow core doors can be readily smashed in with little effort. Walls that are drywall-and-studs can be easily breached. Windows can be broken or jimmied open. Etc., etc. I personally would not try to claim that a room in my house was a "locked container" unless I had taken steps to secure it over-and-above the typical room in the typical home. Your mileage, as they say, may vary.
Let's face it, much of safe-storage, modulo a couple of well-documented examples that have been carved out, is a grey area. Trigger locks are specifically called out in the law as compliant, and a locked plastic container was called out in Commonwealth v. Lojko as compliant. So it would seem that you don't need Fort-Knox levels of security that would deter a team of seasoned yeggs to be compliant; you just have to have a level of security that would thwart casual tampering. Again, YMMV, and certainly, many NESers go above-and-beyond the requirements of the law by availing themselves of higher levels of security. Having your guns stolen sucks in all sorts of ways.
As an aside, in some of the commentary on this case, I've seen allegations that Parzick was not a sympathetic defendant. I've also seen a claim that Parzick's defense was merely an afterthought, a "hail Mary" to try to beat a safe-storage charge. Hence Comm2A's frequent observation that "bad cases make bad law"--this case certainly looks like an example.