This is pretty wrong. The view you describe arises from the complete renewal in the history of the Middle Ages that occurred from the 1950s onwards, and which established that the commonly called "Dark Ages" weren't so dark after all.
But that's not to say that there wasn't a precipitous drop in life quality after the end of the Roman Empire. Recent archeological finds have improved our understanding of the details of Roman daily life way beyond what we used to know even thirty years ago.
For a good and accessible overview of the latest finds in Roman archeology, I'd recommend "The Fall of the Roman Empire and the End of Civilization" by archeologist and historian Bryan Ward Perkins.
He highlights how much the Roman world had in common with our own period, most notably in terms of mass production of standardized goods (e.g. pottery), integration and specialization of local economies in a globalized market throughout the Empire.
The breakdown of this Empire-wide integration led to a dramatic decline in standards of living. To take just two examples extracted from the book:
- pottery finds in Britain reveal that before the Roman conquest, the vessels commonly used were all locally produced and of average quality. The integration in the Empire brought the mass-produced, standardized, high quality Roman pottery into the British economy, so much so that all levels of society had access to it (as illustrated by the archeological finds). This competition drove the British pottery industry out of the market, to the extent that by the time the Romans had to abandon Britain, there was no significant pottery production on the British isles anymore. The outcome is that the potteries found in the tombs of the first Anglo-Saxon kings are of a much poorer quality than those of the British peasants five centuries earlier - to say nothing of the Roman-made pottery a hundred years before.
- In the Roman Empire, thanks to mass production of roof tiles, almost every house had roofs made of clay tiles. This provides a host of benefits, notably in terms of durability and improved health thanks to increased insulation from humidity. With the collapse of the Roman Empire, European housebuilding went back to starch roofs - which in addition to be a poor way to protect yourself from rain or humidity can be a breeding ground for diseases and pests. It wasn't until the late 15th century that the prevalence of tiled roofs reached an extent comparable to that of the Roman world more than a millennia earlier.
I really recommend this book, it shows how the past 15 years of archeological finds have illuminated how close the Roman society was to a sort of proto-consumer society; and how much was lost when it disappeared.