Armature Studios has the team that made Metroid Prime. Retro Studios does not. This is a fact. It's not relevant if you like their games or not; it doesn't change the fact that Nintendo hasn't given it to the people with experience.
And yes, EAD lacked the ability and experience to make Breath of the Wild without the learnings and experience of Monolith Soft; why else would they need them? Similarly, Retro Studios lacked the ability and expertise to make Donkey Kong Tropical Freeze without help; and that is a far simpler project than something like Metroid Prime. Retro Studios needed help to make a rather average Nintendo platformer, while EAD needed help in making what is arguably the greatest game of all time.
Metroid Prime's series decline was not my personal opinion as it declined both critically and commercially from the first game.
I am not sure why these things make little sense to you?
You also claimed people from Naughty Dog, Id Software, and Vigil Games? What are their jobs in Retro? Who are these people?
Looking back to a year ago, there was a lot of smoke around people being unhappy at Retro Studios; many expected the studio to close down. This was after about 4 and a half years with not even a game to announce: https://mynintendonews.com/2018/07/03/former-retro-studios-employee-claims-nintendo-is-shutting-it-down/
How is a studio with such low productivity going to make a massive game like Metroid Prime?
Put all of this together with the fact that Metroid isn't an essential franchise from a business perspective - mostly from an image perspective - and what conclusion would you come to? To me, it looks like they are a burden, and Nintendo is looking for an easy and painless way to get rid of them - even if they have to dump a few extra million into it - they'd be far from the first publisher to pull stuff like this *cough-cough THQ/EA*.
On the other hand:
Does it make sense to you that a studio with a lack of experience, lack of productivity, and lack of staff numbers CAN produce a Metroid Prime game without it being mediocre and therefore disappointing?
And yes, I realize I'm the guy with the "asshole argument" here (and my Nintendo-heart does ache that I'm forced to be THAT guy), I'm pissing off Retro fans who treat this studio as a sacred cow and pretend as though they're just holding back all sorts of magic... The fact is, Retro studios have only successfully produced a 2D platformer they co-developed, and a few classic tracks remixed for Mario Kart 7, in NINE years!
Actually, is not about me disliking their games. Is about them objectively making mediocre games. Their biggest games are: ReCore, which was a mess for both critics and players alike; Batman Arkham Origins Blackgate which will not be remembered by anyone; and a bunch of Vita ports. The fact that these guys made Metroid Prime in the past is irrelevant. The truth is, they have shown that right now, in this moment in time, they are a mediocre studio that makes mediocre games. Trying to just even suggest to give them Metroid Prime 4 when they couldn't even handle a 2D Batman game correctly is silly and dumb. I can't sugar coat it for you.
Are you telling me that the biggest studio of Nintendo cannot make an open world? Really? What can't they do? Creating terrain? Modeling things? Add vegetation and water? Designing the world itself? EAD knows perfectly well how to make a videogame. Even if it is an open world. Is just a matter of scale. The most people they have, the better and faster they will do the job. Monolith Soft just so happens to be an expert in open world games and they are owned by Nintendo. If you actually compare both BotW world and any Xeno world, you will realize that BotW has better design, better phyisics, is more polished and is the one that works better in performance of them all. If EAD is not capable of creating an open world and Monolith Soft is so good at it... why Xenoblade worlds run poorly at times (tons of popping), have zero interaction with the enviroment (in Xeno X many objects didn't even have collision, LOL)... but Zelda is excellent? Huh... maybe EAD knows how to do things better than you think. Maybe Monolith helped with its experience, but mainly in manpower. Maybe both studios had a symbiotic relation that helped BotW to be as great as it is. Maybe that was the reason they worked together. Maybe your reasoing is more flawed than AC Unity at launch.
Retro lacked the... what?! Retro did DK Country Returns! A game that was super well recieved by both critics and players! They knew exactly how to make a DK Country game xDDDD They didn't need help because they weren't capable of doing the game. The needed help for the same reason Monolith helped EAD: two people work better than one. Simple as that. I can stomach that you don't believe Retro is capable of making Prime 4, but suggesting that they couldn't make Tropical Freeze when their last game was a DK game and they themselves ASKED NINTENDO TO DO IT is beyond ridiculous.
Going from a 97 on Metacritic to a 90 is not what I would call a decline since all three have an "excellent", specially when we take into account that all three games, while essentially being the same, have many key differences between each other. Prime 1 is the most conservative, Prime 2 is the "weird" one with higher difficulty and Prime 3 is more action based. It's nearly impossible for the three to score the same... and if you're gonna suggest that Prime 2 and 3 should have scored a 98 or a 99 I'm gonna shot myself. I insist: all three games have excellent scores of 90 or higher. The trilogy itself is pure quality.
As for Naughty Dog and Vigil Games employees:
Yeah, these are old news, but they are true anyways. I can't find the id Software one, but I'm certain they did hire a person from that studio.
As for that one annonymous person who speaks for apparently half the team without them saying a damn thing... Well, excuse me if I don't trust your source, but I won't give it too much credit. As for the other employee... he just thinks management could do things better. Many succesful places have the same problem and we don't take our hands to the head.
Next... we don't know if the project they have been working on has been a failure. You like rumors a lot apparently... so why don't you believe the one of the Star Fox Racing game? The game could perfectly have a lot of work done and be ready to be announced, but after what happened to Metroid Prime 4 maybe it was frozen and MP4 is now a priority. Frankly, I would believe this more than Nintendo giving Retro MP4 to see them fail and get not only backslash from the failure of MP4, but for destroying the studio.
Retro Studios has currently 139 employees... that have a linkledin account. Let's say, thinking low, that the actual number is around 150-160. That's more than enough to make a Metroid Prime game. Other studios have done games as big or bigger with the same or less people (Monolith Soft with both Xenoblade Chronicles X and 2, for example).
Again: all you say (lack of experience, lack of staff and lack of productivity) is mostly false. The studio is pretty big in numbers, it has experience and the fact that you don't know what they have been doing lately doesn't mean they are doing nothing.
But as for your question... if Retro fails in delivering a great MP game, their future will be clowdy, that's for sure. But that doesn't mean that Nintendo is giving them the project because they expect them to fail xD
As I said, all of your arguments are still debatable opinions or straight up nonesense. And I think I'm done here. I said all I had to say. Good evening.