You really can't bring Metacritic into this, especially given how that alone is a sample size of only a few people (critics). Even then, I would counter that a "79" would never be considered a "passing grade" at most institutions, while the actual user score is lower and checked as "mixed" reception. Even if that's the case, it's still the lowest-rated Metroid game ever created, on par with Metroid Pinball, in a series that often is listed in the most critically acclaimed games ever made, and Nintendo themselves admitted that sales of Other M did not meet their expectations, which is further disappointing if you consider it was the most expensive Metroid game to make with some of the lowest sales of the series.
But I think you're also entirely missing the point of the criticisms that KingBroly and others have, and I understand this too. This is not an example of hating something like Skrillex that you never liked... this is more akin to having something you really love mutate into something you loathe. I can relate, heavily, as I've watched my favorite survival horror games turn into mindless, scare-less action fests riddled with QTEs. I've watched a superhero I idolized as a child sell out his wife to the devil and betray his loved ones. I've seen franchises thrive and die as incompetence sets in, standards are lowered, and a new generation who never played the good games has no standard to compare against and thinks that a lot of things are "great" when there's an entire history of excellence they've never been exposed to.
The reception of Other M was mixed, and a vast number of people, an unacceptable number, felt it was flat-out BAD. Nintendo felt so as well. The sales weren't there. The reception wasn't there. The response wasn't what they wanted. Even those that love the game have to concede that there are major, fundamental problems with the game at its very core, and reception has not improved for the game. Those that hated it continue to do so more and more, and it's legacy is approaching that of the Star Wars prequels.
In fact, the Star Wars prequels are a good example. They, too, have mediocre-to-decent scores on Rotten Tomatoes, a fair share of defenders and fans, and many people genuinely like them, despite their flaws, but the general reception was that the series in George Lucas's hands lost its way, became embarrassing, lost what made it special in the first place, added in loads of style and bad acting and very little substance, and old fans became jaded and disappointed more and more and more with it. I've even read critics who liked the game at first change their minds on Other M after thinking on it over the months. It happens, where an original impression, and the flaws and plotholes and awful parts, don't really resonate until you reflect on it over time.
Like Final Fantasy 13 has its fans, that game was still not up to the usual standards. Like Devil May Cry 2, it wasn't what fans wanted. Like Indiana Jones and the Crystal Skull, it may have made some money and had a mixed reception, but it's legacy has not been kind to it.
"Other M" is that to Metroid. Sorry if that bums you out and you like it, but, well, yes, many people, I'd even say a majority, walked away from Other M unimpressed, if not outright disappointed and angry at what happened. Nintendo themselves were disappointed, and I don't blame them. It had some good ideas, but it thoroughly botched the execution.
And, well, yeah... Other M even has the "Other M: The Movie" mode, so Nintendo made their movie... too bad it wasn't that great.