Ugh. I'm going to explain why you're wrong and explain how Prime poisoned the entire franchise in the most succinct and eloquent way I can. I got out of fucking bed to do this, so read it.
FPS is fundamentally flawed for a game with an emphasis on exploration and platforming (I dislike it for any game, but that's another matter). You can have a 3D Metroid, but to keep the series' DNA intact it needed to have been presented in the third person.
The great irony of FPS is that it completely detaches the player from the character and de-immerses you in her plight, and removes any sense of proportionality to the experience both in pathos and raw mechanics because we don't see our character in relation to the environment (Briefly seeing Samus in third person when switching to morphball was such a cosmic tease as to induce madness). This might be fine for 90's gimmickry to wow people with emerging technologies -- "Wow, it's my point of view as I shoot nazis!" -- But for a more depthful experience, for a character driven experience in particular, we simply can't forge the necessary connection when experiencing the world literally through their eyes. This is the great farce of FPS. (I won't even go into the mechanical clumsiness that arises from the inability for peripheral vision to be represented on a flat television surface)
We also have the problem where many classic staples of Metroid gameplay specifically require third person perspective -- I'm not just talking about the screw attack, but environmental puzzles and platforming demand a better sense of spatiality than FPS provides. This is borne out by Metroid Prime's own designers, who had no choice but to clumsily wedge in awkward switches to third person perspective with fixed, highly controlled cameras whenever they wanted to do a morphball segment. These segments weren't a design victory but an admission by the designers of the game's flaws. Controlling, overdesigned shit like this works against the core of Metroid and shatters the entire fantasy in a single stroke. When you have a game that has a real sense of mystique and isolation, where the onus is on the player alone to navigate its depths -- you simply can't have the designers step in and jerk you around or show you things whenever they decide it's necessary. And if the premise of the gameplay means that it's necessary, then re-examine the fucking premise.
Prime represented a pointless changing of the formula and shifting of priorities that no one wanted or asked for, and after the third dull, unengaging, boring game failed to build an audience, it left the series without an identity. I submit that Prime is responsible for the destruction of the franchise. Other M is a bi-product of Prime's systematic removal of the series' identity over a generation.
If they wanted to make a FPS exploration game with terrible lock on combat and clumsy, vague platforming they should have just done so and called it something else.