This is actually one of the things in ME that really bothers me, and I don't mean like the physics nitpicking I usually do. No, this is something that actually bothers me about the MEU. Humans are driven by their curiosity, we always want to know more, no matter if that knowledge is actually useful or not. You're trying to tell me that the entire galaxy is dependent on technology that nobody understands? That nobody is even trying to understand? The codex tells us that eezo is naturally created during supernovaes. That tells me that it forms during high energy particle collisions, which means it can be created in a powerful enough particle accelerator. Your telling me that nobody has ever done that? That nobody is trying to see at which energy levels, through which interaction it gets created? When it decays? Through what forces it interacts? Does it need a special gauge boson to have it's mass changing effects? The notion that everyone in the galaxy has been using a ressource, for thousands of years in some cases, that they have no idea about what it is or how it works, drives my inner hobby particle physicist insane. Of course I don't expect some poor BW intern to make a page one rewrite of quantum field theory. I don't care how eezo works, but the people in the MEU should and they're not even trying. The same of course applies to the mass relays and the citadel. You have been living on a station for thousands of years and never bothered to fully explore it? And then you suddenly act all surprised when an advanced alien species shows up, that you already knew existed, because you were using the evidence all the time, but never bothered to actually look at. Especially considering the Asari were chosen by the protheans and had a prothean beacon on their homeworld giving them acces to advanced technology for almost 3000 years. Humanity gets a pass for beeing the new guy, but Asari are truly the most retarded of the lot.
If the informations about ME4 are reliable and it will really happen in another galaxy, then we must have some development in building mass relays. There is no point in using a mass relay built by Reapers to run away from them, because they would know sooner or later. And I agree with Asari dumbness in this point if they had all this information at their noses.
You see, And i mean no offense here, You just look at the MEU in a scientific point of view. Not a storytelling point of view. I am aware that Eezo is forged during supernova, But not much of it is known, How it's created. BUT, There were some attempts to create FTL travel by the alliance near a station near Pluto. Or something like that, Don't really remember well. Before they discovered the ruins. Point is, There are a lot of unknowns. It's like, Someone threw Einstein's photo electric papers or Planck's law papers or many other scientific research that led to the invention of the laser, Away to you for free and you don't know what or who that is. But you keep experimenting the technology trying to make use of it and trying to understand it. It's the same case with Eezo but on a larger scale. Remember when they said in ME1 that the Prothean were so close to understanding and solving the mystery of the mass relay network? Anyways, I think that Eezo, Dark Energy, Space-Time Dilation and many other concepts were originally intended to be parts of the trilogy's ending as Drew K have stated in an interview. It'd have been a grand finale to the trilogy that would explain a whole lot of things about Mass Effect. A gigantic mass effect 1-like twist that would leave you absolutely stunned. Point is, The mysteries were there for reason, Not because BioWare was lazy. At least i think so.
ME3 ending's are just a decoy, BW and EA are telling us that they don't want do reveal anything for now because it will sell more later if they reveal something - as little it can be - later. And so on, a bit in ME4, some more ME5, creating more questions in the process. The doubts they create in our heads are the business machine, not the answers.
As for the council being dumb, It has been stated in the codex that the reapers were a myth to many primitive civilizations and that's why the council didn't believe it. As for the continued disbelief of the reapers, It's just that they're in denial, Just like those conservatives who won't admit that the Earth is dying and that global warming is real.
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I don't think the council are dumb, neither in denial, they just don't want to reveal their actions as Shepard was working with Cerberus in ME2, and in ME3 **** just happened too fast for a plan. They can't accept Reaper existence to the general public too: "hey people, there are some motafuqing machines coming from dark space as ships with length of 2km that can destroy a dreadnought with one shot, but don't worry, keep living and working while the end of world aproachs". Anything had to be done in the shadows, panic of the unknow wouldn't help the cause.
Again, if ME4 happens in Andromeda Galaxy, the council must have a hand on it.