The plot has been pretty well thrashed out by now, so I'll just say that I agree with every word of the TV Tropes analysis, that I had to walk out of the room in anger or due to cringe multiple times (to this day the only game in 31 years to make me do that) and that this game was a major reason I refused to buy a Wii U at launch, the salt was still that strong.
I'll also add that when people are still upset 5 years later, you know you fucked up. Most things are forgiven and forgotten in a year. Only the very worst ones and biggest disappointments linger like this (see FF13), and tons of Metroid fans are still upset. We still get threads like this all the time, and they always attract angry posts (like this one).
I will say, though, that I don't understand the view that 'the idea to give Samus a character was a good one, but executed horribly'. Why? Why was that a good idea? It seemed like a fucking terrible idea before Other M, and a disastrous one afterwards. Samus is one of the all-time 'inhabitable' game heroes. Not a blank slate, no, but close, and inhabitable. Prime's visor is one of the all time greatest examples of literally putting you in the hero's shoes. There's no reason to mess with that, that was a pretty core feature of Metroid.
Secondly, Metroid games have never had particularly coherent or involved stories requiring dialogue or conversation. Even as a huge Metroid fan, Samus' back-story was generic at best, and cheesy D-list comic book sci-fi at worst. This is not the strength of the Metroid series, and thankfully none of it is ever really seen in the games (save the end of Zero Mission, where it's equally weak). The famous manga is fairly abysmal, but you could ignore that if you're just into the games. This story-writing stuff is just not what the people who make Metroid are good at, and it's not what people want or expect from it, and that's fine. They always seemed to know that, and just put Samus on her own on a planet with bad guys. When they went further, Fusion, results were mixed and criticised. So why travel further in this direction? Further towards shite blockbuster AAA games that live by big-budget cutscenes and shit gameplay? When you're not even good at the cut-scenes but are amazing at the gameplay. When you can plop Samus on a planet on her own and fans will be happy?
I mean, take the Legend of Zelda. They're actually properly narrative driven games, with plenty of dialogue and character interactions, and yet people think Link should forever remain a blank slate. That's a situation where it would make sense, if they wanted to, to introduce a personality to a long-loved character, but I see both sides of the argument there. With Metroid however, there was just no reason for it, and I can't understand anyone who wanted it, or who defends it now. It was clearly a bad fit for this particular series of games, one from a guy who decided he wanted to play at being a Hollywood writer / director and had had too much success for anyone to tell him what a shit idea it really was and that his writing was sub-fanfic level garbage. If Nintendo had wanted a blockbuster narrative cutscene infested game like the 360/PS3 had, they should have done something from scratch.
And as always, if Nintendo cared about their girl fans they'd strike Other M's story off as no longer cannon, and admit it was a bad mis-step. It is blatantly sexist, and makes my skin crawl to this day. If Other M 'stands' in Metroid's fiction, then I don't believe Samus' character will ever be redeemed.