This is a fascinating question for a couple of reasons. One of them is what you define as “the final decades of the Western Roman Empire.” I’m not going to debate thay here because that’s not really what you’re asking, but there are more points at which you could say that the empire ‘ended my than September 4, 476 (the ‘traditional’ date).

A second reason, the one that’s more at the heart of what you’re asking, is this idea of awareness of things ‘coming apart.’ Awareness is a funny thing because it’s all based on your frame of reference and what you can access. If we use that date of 476 as an anchor for the sake of convenience, what exactly would folks have as a frame of reference?

Well, one date that sticks out is 410. On the one hand, that’s a date in living memory. Granted, in the intervening 67 years there was enough time for a couple generations to be born and grow up, but that’s still a time that some living folks could remember. I stress living memory because word of mouth is how most folks would know their history. Yes, there were books, in fact there were a lot of books we don’t have surviving today, that folks could look to for stories of the glories of the Empire. However, you’d both need physical possession or access to the book and a person who could read in order to get at those written memories. For most folks, what the elders in your town or village remembered was your frame of reference though you’d have at least a vague sense of the old power of the Empire.

I pick out 410 because in that year Rome was sacked by the Goths. The “golden age” of the Empire was a few centuries gone by the time 410 rolled along but that sack really signaled a moment of Roman weakness. The Empire was able to rally, but that post-410 world would have meant something different to your average folks. It signaled that whatever the Empire had once been, it was now truly vulnerable.

In the intervening decades bits of the West began to fall off into self-directing “Barbarian” Kingdoms, but it’s honestly, in many cases, an open question how much this impacted life on the ground. There were certainly land seizures but likely not wholesale random slaughter. While this would be unpleasant at best for the mass of the people, it’s good to keep in mind that the Roman Empire was not all sunshine and roses for its non-elite residents. Life under a Frankish or Visigothic warlord might not have been all that different for the mass of the populace than life under Roman governors. It was certainly a time of violence and danger, but that doesn’t make 476 any different than, more or less, the 60 or more years before or after.

For the average Roman citizen I doubt that there was much more of a sense of “doom and gloom” and that things were “falling apart” on September 4, 476 than on September 3 or September 5. For the elite, though, folks who had money and lands that they saw slowly (or quickly) drifting out of their control, folks who had to grapple with a loss of political domination, folks who had a frame of reference that perhaps helped them understand better the gulf that separated them from their 2nd century counterparts, they almost certainly felt the gloom.

On a personal note, I feel much more sadness for the majority of the Empire who just continued to live difficult lives under new elites than I do for the privileged upper echelons of Roman society who saw their power collapse.

If you’re looking for readings, I recommend the following in no specific order: Kulikowski, The Tragedy of Empire: From Constantine to the Destruction of Italy, 2019 McEvoy, Child Emperor Rule in the Late Roman West, 2013 James, The Franks, 1988 Goffart, Barbarians and Romans:Techniques of Accommodation, 1980 (though I very much disagree with it) Grey, Constructing Communities in the Late Roman Countryside, 2011 Anything by Peter Brown.