There are many reasons why I hate the term, least of all that it makes people refer to Metroid as 'Metroidvania,' despite, you know, it being the originator. Metroidvania is a sub-genre title given to it as a combination of Metroid and Castlevania 2 style Vania games. I've tried to use the term 'Metroid-like' for games that are closer to Metroid recently as well.
But overall, it doesn't describe what the game is, or what you do. That alone probably limits the reach of those games, despite there being a lot of them. The game that creates the proper term for it will be a Breadwinner. I hate that Nintendo can't do it themselves, also, considering they made it. It speaks volumes to their lack of creativity regarding the series that they can't even define it other than 'Metroidvania,' which lowers the status of the series as well.