I'm going to assume that by 'dark ages' you mean the early middle ages; that is, the period in Western Europe from the fall of the Western Roman Empire in 476 to roughly the turn of the millennium. Historians largely reject the term 'dark ages' because it implies a) that we don't know very much about it, which is absolutely not the case (we know literally thousands of individuals from the period, plus plenty of culture, laws, literature, history etc. etc.) and b) that it was a sort of period of regression, where nothing good ever happened. Your question seems to presume that the latter view was true - that life in the early middle ages was 'shitty' and obviously even 'shittier' as a commoner, but I'm here to happily inform you that you're wrong. In fact, in the view of some historians, the early middle ages were the best times to live in as a commoner before the modern period.

This argument goes that when the Roman empire collapsed, so too did many of the complex systems it supported. On the one hand, this included the system of inter-regional trade (which piggy-backed on state-subsidised transport of the dole and army requisitions) which gave people from across the Empire access to mass-produced goods, such as olive oil, fancy pottery and much much more. But it also included the complex tax-collecting system which allowed the army to be paid and, crucially, allowed local elites access to the power of the state. Without the Empire, local peasant communities paid far less (and sometimes no) taxes, tribute and other exactions to local elites and became, overall, more egalitarian. Of course there was huge variation across Europe, but as a commoner you could expect to own your own farm, work when and how you wanted and live in a village where every free adult male had a pretty equal voice in the running of local affairs (obviously things look less rosy if you're a woman, a child or a slave, as is the case in most of human history). You would, however, be very materially poor by our standards, and indeed by Roman or later medieval standards. Most of the things you owned would have been made locally, or even by your own household; you would be essentially a subsistence farmer, at the mercy of famine if it struck the whole village/region; there is also far less of a chance that you would ever live in or see a city.

Throughout the course of the early medieval period, aristocracies become more and more powerful again, particularly with the rise and spread of the Carolingian Empire in the eighth and ninth centuries, who in their heartlands had established a fairly tight grip on peasant communities by c. 800. Eventually, by the eleventh century, peasant autonomy on the earlier scale was rare in Europe, although in contrast inter-regional trade, agricultural productivity and urbanism were all picking up speed again. Whether this is 'better' or 'worse' is very much a matter of opinion: is it better to be materially more comfortable by less autonomous personally and politically? Or would you rather be poorer but have more control over your own actions and destiny?

If you want to read more about this, the foremost authority on this is Chris Wickham, who goes into way more detail than you'll ever need in his Framing the Early Middle Ages (Oxford, 2005), which also produced a wide range of responses, mostly in academic journals. A much more digestible introduction is in Wickham's The Inheritance of Rome (London, 2008), chapters 9 & 22.