Probably saw it coming, but I can't get behind this line of thinking. While I agree Link shouldn't talk (though I'm not completely against the idea), I disagree with the notion that all the characters are just avatars, especially Samus who has the most personality out of all the Nintendo characters, except arguably the Starfox characters. Ignoring Other: M's existence, Samus has been talking ever since Super Metroid, and she was very dialogue-heavy in Metroid Fusion.
There's also the unavoidable reason that your "avatar" will often do things that you yourself would not do in the first place. This is immersion breaking, and is often the reason why story-tellers have forgone silent protagonists in the first place, because completely empty protagonists are hard, if not impossible, to implement in a narrative.
The best thing about Silent Protagonists is the ability to flesh out their character by yourself and then debate about it online. You often feel closer to Silent Protags because you personally invested a lot of your time to fill in the holes.
Also, Snake has dialogue in Brawl.
Snake didn't interact with anyone through dialog in the story mode though, all he said was "Kept you waiting, huh?"
I don't mind Samus' dialog in Super Metroid because it only happens at the start of the game, and it's really more or less just a "the story thus far" segment. After that Samus is completely mute, had there been dialog through that game the atmosphere of places like Maridia and the Wrecked Ship would have been completely ruined if we had to stop to listen to some stupid thing about how Samus feels like she always did in Other M. Likewise with Metroid Prime, there wasn't a single piece of dialog in that game, at most there was the Chozo stories you could scan, and that game's atmosphere would also have suffered heavily if Samus had to stop up constantly to give her thought on everything. These two games are also commonly considered the best Metroid games, and part of that comes from the fact that it's so easy to immerse yourself into the atmospheres of the places, it's easy to pretend that you're in Samus' shoes.
So what about Fusion? Guess what, I'm not a fan of constantly having to stop up because I have to be told what to do, Metroid is for me about the non-linear gameplay, the exploration and atmospheres of all the places, and Fusion heavily lacked on those departments because Samus was put under the boot of the Federation. Which is funnily enough also Sakamoto's touch, and how he has decided to run the main franchise since Gumpei's unfortunate death after Super Metroid, Zero Mission luckily being an exception. Fusion is still a good game, but Metroid fames are usually great and incredible, not just good, and I feel that Sakamoto's need to tell an underwhelming story is what keeps it from being better than that.
Samus is best kept mute and alone, Metroid is a franchise dependant on exploration and atmosphere, something that's easily taken away by an overarching story, and without its core elements what makes Metroid stand out from the rest of the crowd?