The PGE 3rd edition mentions the horror of the siege, Where were you when the Dragon Broke directly references what happens when you turn the Numidium on, the Warp in the West describes the distortion and fracturing caused by the Nimidium's Dragonbreaks, the Mysterium Xerxes alludes to the existence of parallel places (such as Lyg).
Admittedly, it's only one of Kirkbride's quotes which outright says it's ongoing, but the argument is supported by everything else we know of Dragon Breaks.
Isn't that what's done on a daily basis? Western powers are still paying reparations for the actions of ancestors centuries dead, to the descendants of victims who are entirely removed from the crime. Time does not absolve a nation of it's crimes in modern ethics (though i personally think it should).
Yes, but we haven't SEEN that threat. There's been no ramp up to justify suddenly turning the Thalmor into the 'big bad'. That's the problem here. Things like Mehrunes Dagon, Dagoth Ur (sort of) and Alduin have been alluded to and built on over multiple iterations. They don't just jump from being political oriented, racist jackasses to cosmic dangers at the drop of the hat (though admittedly, Dagoth Ur went from being a dangerous volcano to a demon-god living under said volcano).
The Thalmor ARE a serious threat. Yes. They are probably the biggest threat around (especially since the Nimidium is elsewhere, and mostly broken). But a threat like that needs build up, it needs development and scope. You don't just introduce it, not explain any of the threat, offer no build up, and then suddenly 'Bam! They;re super bad guys, kill them!'.
And that's the issue here. It's not whether or not the Thalmor are ultimately bad (they are. They're lunatics who know enough to be dangerous, but not enough to succeed) its whether or not they've had enough development and significance to justify rushing to the end of their story.
They haven't. Not without some absurdly ham-fisted exposition delivery in the next game. Their story is set up so that it can't be told in one quick go, it's going to take time, and any attempt to rush that for the sake of getting it done is going to cheapen it.