The problem with both is the
beyond obvious ROFLstomp on the setting that crushes EVERYTHING in just a few decades.
There's nothing you can do ... except give up and surrender to the inevitable.

Because it's not YOUR game ... it's
somebody else's property and they're going to wreck it simply because they can (in a fit of ego/pique).
It's almost as if "filling in the map" for all of charted space was a ... mistake ... or something

such that the Third Imperium was "bounded" on all sides by other polities with nowhere else to grow/expand to, therefore the only "logical" thing to do was to ... blow it all up.
I mean, seriously, with the Wave especially, you're talking about something so powerful (and garbled) that it can wipe out not only "civilizations" but entire biospheres

pretty reliably, leaving only devastation in its wake as a
Galactic Reset Button (which is how many sectors?).
Talk about a Weapon of Mass Disruption.
And then there's the Virus ... which just proves the point of an old Murphy's Law poster line.
If builders built buildings the programmers write programs, the first woodpecker to come along would destroy civilization.
Not only was the Virus
like the Borg (ST: TNG) and
like the Founders (ST: DS9) ... it also developed psionics as a machine intelligence, which is just DERP.
Seriously, if
Traveller needed a setting/milieu featuring "the collapse of civilization" there's the end of the Rule of Man/Ramshackle Empire/Second Imperium going on into the
Long Night (-1776) sitting right over there in the OTU history. The trigger was a financial crisis, leading to centuries of a slide into the darkness.
The Long Night is a much better "sunset on civilization" story, simply due to the fact that the causes are self-inflicted (parochial greed, vulture capitalism, etc.) combined with the inherent friction caused by jump lag in communications (making "far away places" REALLY FAR AWAY).
I would argue that during a civilization collapse event such as the Long Night that any world lacking Atmosphere: 5, 6 or 8 and Hydrographics: 4+ would be a candidate for a
Die Back World. Any world lacking those features AND with a Population: 6- would DEFINITELY become a Die Back World in the absence of interstellar trade to sustain the world's population ... although the collapse could "take a while" ... but I'm thinking in 2-3 generations, it's all over. Everyone who can leave has already left ... and those who didn't are "trapped" and CAN'T (or simply, won't) leave and are the last of their kind as their civilization dies.
Population: 7+ worlds would be the only ones that could potentially "sustain" their civilization regardless of (other) UWP codes, but even then they would need to have enough Tech Level to be capable of self-sufficiency without needing interstellar trade. In some environments (such as asteroid/planetoid belts), that puts a premium on fusion power technologies/industries to sustain life and life support.
Which means, that as soon as people can see the "writing on the wall" following the Market Crash™ ... there's going to be a RUN on interstellar transport services as those with MEANS flee the places that won't survive to the places that will, causing a Mass Migration among the stars. Think refugee crisis in terms of BILLIONS of people, just to get an idea of the size and scope of the (entire) catastrophe across the crumbling of the Rule of Man/Ramshackle Empire and you'll start to get a sense of the level of desperation among people for "the last flight leaving the planet" in those times as the Long Night began to fall and settle in.
Being a Traveller in that era wouldn't exactly be a "safe" profession ...