To think that the general populace would just sit there and take it for three eras is pushing the realm of believability, even in a fantasy game.
Not really. Ancient Egypt was ruled by a line of royalty and pharaohs for about three thousand years, until they were kicked out by the Roman Empire. The system of Monarchies/Dynasties, in which the privileged few rule the vast majority, is the way most countries on Earth worked for many thousands of years. Individual empires came and went, but were typically replaced by new people doing the same thing. I haven't played Skyrim or read the books, but for a more relevant comparison, as I understand the Mage's Guild went under and was replaced by other, similar factions.
And while most places on Earth saw gradual increases in technological development, in things like metalsmithing and plumbing and whatnot, things didn't really kick off or change significantly outside of the occasional big discovery until a couple revolutions in the past few hundred years. It's a tiny period in history, and it still doesn't apply to the whole world. Native Americans lived in the region, and did not have significant technological advancement, for longer than the entire known history of Tamriel. They were still using bows and arrows tipped with stone.
While part of technological advancement is discovery, part of it is also need. Gunpowder let us do things we could never do before. The early stages of gunpowder would not be very useful in Tamriel, against the argument of "do a small portion of what mages can do, only you can't really control it and get to blow your hands off". If a new technology seems inferior to existing options, that line of development may never see fruition. I'm not saying that the advancement of technology wouldn't or couldn't happen, or that it's even unlikely, but that it's in no way an inevitable guarantee, especially with the important phase of "things we never had before" being muddied by magic. Neither the duration or forms of rule in Tamriel or its persistence without high technology are unprecedented or even unusual.