I'm not! I specifically used the term 'Metroid-like' rather than 'Metroidvania' because Axiom Verge does not feel like a '-vania' game. Its Metroid roots are so very obvious, and it hasn't taken anything from Castlevania as far as I can tell.
In general I'll refer to titles in the genre as 'Metroidvanias', and I'm sure I've done so on GNamer in the past. I used 'Metroid-like' instead here for a very specific reason.