I'm just curious. Why don't you?
Sixty years ago, the Chinese were regarded as technologically backwards politically chaotic agrarian weaklings. Now look at them. America used to be defined by its policy of non-intervention. Now look at us. Before the Franco-Prussian war, the stereotype was that Germans were poor workers, spent all their time relaxing, and couldn't fight worth [poopy]. Before WWI, France was a feared military power. Stereotypes, and the realities they're based on, change dramatically over time. Why do you think this wouldn't be true in Tamriel?
Sixty years ago, the Chinese were regarded as technologically backwards politically chaotic agrarian weaklings. Now look at them. America used to be defined by its policy of non-intervention. Now look at us. Before the Franco-Prussian war, the stereotype was that Germans were poor workers, spent all their time relaxing, and couldn't fight worth [poopy]. Before WWI, France was a feared military power. Stereotypes, and the realities they're based on, change dramatically over time. Why do you think this wouldn't be true in Tamriel?
Well, first off as I am sure you have heard many times. This is not Earth. All those changes not only do not reflect a change in culture for that demographic but were due to rapid technological and economical developments alongside incredible cultural changes the likes of which is not happening in Tamriel. Secondly how they were viewed does not really affect the people. China also was a very advanced society at one point. In fact the most advanced in the world. They lost power and fell into dark and corrupt times in which they lost the power to defend themselves. They pulled out of that and are now getting back to where they believe they belong. At the top. What changed about them culturally as a people because of that? Not a whole lot. They are still very prideful in their country and still hardworkers, this is close grounds for stereotyping though.
With Tamriel in mind, Well the 3000+ years of time in which the Dunmer stayed the same culturally for the first part. Secondly 200 years is not even one generation for Mer. Lastly the events do not make sense for the changes to have occurred. If the Dunmer were on the run who is teaching them more magic skills? If anything in general they would be picking up swords more often or using makeshift weaponry and becoming survivalists. Once together they would probably start getting a society together that was training itself for war to reclaim their homeland. They do not have a single Combat skill. Redguards have been bad at magic in every game that I am aware of. Even in so far as it is a natural aversion for them to dislike magic of the 'Magnus' variety. They have been this way since they arrived on Tamriel. 200 years of events that were not that big for them would not change this imo. They did not experience a Red Year or anything of that impact that I am aware of. Why the dramatic change? I doubt the Bretons would have been training the Redguards as an entire people in magic. Altmer are less in tune with magic now as well. They no longer are balanced power-wise, by their weaknesses. Also their selective breeding processes alongside their pure merrish descent no longer seem to give them disease resistance. Why is that? I could go on and on about the poison resistances and such but I won't.
It is just game-play mechanics. There is little lore in the racials.
There are many holes in the whole 200 years of change thing, especially for changes this dramatic in some cases.