People focus too much on the "escape Mundus" part of Altmeri culture in general. For most of Tamriel's history, they were perfectly content with sitting in Summerset. As a whole, the caste system is probably a more important aspect to focus on, though I'll be surprised (and disappointed) if it's not backed up by religion.
I think we focus on the "escape Mundus" part of Altmeri culture at the moment because there's a source out there telling us that this is the long-term plan of the Thalmor. You're right, the Altmer were productive citizens of the Septim Empire for 400 years and more, but as of right now the Thalmor control what the Altmer position on existence happens to be. We're not pointing the fingers at the Altmer as a race, but the Thalmor as a government. As far as I know, no one on this forum has advocated genocide against the Altmer (yet, anyway, because I figure that someone will have to say it now that I've said we won't).
Also, on the lore forum, it's no surprise that we discuss the creation of Mundus ad nauseum here. With the focus of most games put on either human races or, in the case of
Morrowind, a mer race with no love lost toward the Altmer, it's not a surprise that most of our information regarding the Altmer comes from their ideas about creation and divinity. Creation is the one point where all races are connected, as they all came from that creation even if they have different ideas of how it came about, or what it really means.