While what you stated is indeed true, let me make another counter argument.
There has never been lore of mursaats helping humans and whatnot (the white mantle does not count as it was a servant-god relationship, it was not mutualistic), it would not make sense for the Exalted to be the mursaat after all the antagonistic role that has been done in guild wars one (especially with the last encounter with lazarus).
On the other hand what you’ve said made me think of the possibility of Seers being the mysterious civilization (none of their writings can be deciphered, a dead speciemen was found in divinity coast in guild wars and they helped other civilization overall by finding the mursaat’s weakeness and they probably existed at the time Elder dragons roamed Tyria)
Why does that matter:
If you look at the last mastery for the Exalted (Wyvern defiance) it may give some info on the relation this species has with dragons (assuming gw defines wyverns as dragons).The Seers are one of the most ancient civilizations and had the longest history of conflicts with one of the strongest civilizations that aimed to rule Tyria; even after losing the war they did not go extinct, but rather slowly declined in population (according to gw 1 lore); this means that likely they endured through the elder dragons era. Had they survived to the current time, it would make sense for them to be the ones teaching the allies on how to compete with these draconic beings as they have previously done for the mursaats.
As it stand i believe either the Seers (very similar in look to the mursaat) or Margonites are viable options. i do not believe the mursaats could be the exalted simply due to their antagonistic role.
It’s interesting how most people think the Exalted refer to the Mursaats, but i’d like to make an argument that it is just as likely for them to be traitor Margonites (like the Lost), which were barely introduced in guild wars 1 lore (and could have been developed on much greater extents). For those who are not familiar with their lore, The lost and Apostate (correct me if i named the wrong margonites) are two of the Margonites that betrayed Abbadon, in order to save their race from his corruption.
Unlike the Mursaats the margonites were never decimated (yes they were initially sealed within the Torment with Abbadon, but after his very short lasting* release they might have escaped?). Kormir could have forgave these individuals and cleansed them from Abbadon’s corruption (the lost actually helped a bit in gw side lore). It should also be considered that gw2’s Season 2 (and possibly HOT) includes a significant amount of lore on the forgotten, who are known to have some kind of antagonist relationship (based on random gw lore) with the margonites.
In an interview with WP, Leah talked about the Exalted as a “group” (emphasis on group) rather then a race and whatnot (which would make sense if it were to refer to the traitor margonites).