So, why no one ever mentioned the Andromeda Initiative in the trilogy?

While I agree any choice would have been divisive, they should at least have the stones to admit when they retcon something.  They should own their choices.

There's no excuse really. It should have been mentioned in Luna's planet description, or Cerberus Daily News, or one of the news segments on the Citadel in ME2, or in some codex entry. I can buy that Shepard never mentioned it but the fact that we never saw a single written or spoken word about the largest, most expensive, multi-species venture before the Crucible is ridiculous.

That being said, I've already long accepted that the opening of this game would be nonsensical like ME2. There was never gonna be a valid explanation for being in Andromeda. Might as well hope that Bioware does something good with the new setting.

You know, that brings up an interesting point.

ME1 has a mission ON LUNA!  And those trailers show the...shipyard?  Where these arks were built were in plain view from there (with Earth in the background as well)

Where was that in the Rogue VI mission?

It could be.  But the orbital shipyards building the Nexus and the Arks should have been in view.  And construction should still be going on in 2183.  Yet it doesn't even get a mention?

Because they pulled it put of their assess

Of course Joker mentioned it. Shepard was just too damn busy flirting with Liara in the back room of the med bay. Chakwas, are you eavesdropping?

I say they should just send out a quick patch to the ME2 Codex mentioning the initiative and be done with it.  ME2 Shepard could even have gotten an email from Alec Ryder while he/she was unconscious saying goodbye that he/she only gets to read after going onboard the SR2.  Since Shepard generally never mentioned his/her emails in conversations (even when Ka'l Reegar died in ME3), there should be no expectation that he/she would talk about a goodbye from an old N7 friend that no one else know on the ship.  Bioware could ship the patch as part of the ME:A package and let people apply it if they want to.  Problem fixed.

Really... people say there's "no excuse" for Bioware not mentioning this in a game that was written years before the idea of doing a 4th ME game was even a glint in Bioware's eyes?  Come on... get real.  Since people want to be so pickyune... they could even extend the patch to the ME1 Codex to mention the facility on Luna... although I'm quite sure the Codex doesn't (and shouldn't) mention every facility located on every planet in the entire galaxy anyways... not to mention that, in the entire ME1 galaxy of billions and billions of space-faring people and all sorts of commerce going on... we NEVER see another ship of any type flying in orbit around any of the side-mission planets at all.  The ME1 ingame entry for Luna does say that the moon was home to 4.1 million people, yet we only saw evidence of 3 buildings on the area of it we explored and no sign of spaceships in flight over it while we were on it... and I didn't hear of anyone complaining about it while playing ME1.

Maybe it did come up between Shepard and Liara or whoever... you know as bedroom chat after the screen faded to black.  We just weren't privy to absolutely everything every character said to each other during the game... what's so hard to headcanon that much?

If the Andromeda Initiative was a secret venture on an uncharted world, that would have been fine as to why characters don't know about it.

Mine was finding out what happens when you mix dextro-protein and levo-protein with Tali.

I myself am not a fan of headcannon (only cannon for me) and i also really don't feel that we need to use this in this case. As you stated, it is totaly unreasonable to want the Andromeda Initiative to be referenced in a game that was released years prior to this one (either be it ME1, ME2 or ME3).

It's liked complaining about about the portrayal of Batarians in ME1 before Bring Down the Sky, or the Collectors/Drell ausence from ME1 to ME2, or that the Reapers didn't have any trouble with eezo core discharge in ME3.

I really don't understand the need to "lose your head" for something that can (and probably will) be easly explained in MEA.

Sorry, if I'm sounding like I'm losing my head... I'm not and I agree with you.  Bioware may a good explanation, a poor one, or even not give an explanation at all... and even that doesn't matter to me.  I am perfectly prepared to just throw the old lore in the trash and allow Bioware to start fresh with this Mass Effect game.  In fact, in many ways, I'm looking forward to learning about some "new lore" in this game... I'm getting a little tired of just replaying the old Mass Effect Trilogy.