The problem is genres are being mixed and it's hard to describe them. Also add to that that no one can really define what a rpg is. Everyone has a different opinion.
The RPG genre is defined. It is much more some players want to label RPGs games that are obviously not RPGs, stretching and inventing definitions to suit their conclusions.
This includes the project of delineating RPGs by the means that can be used in RPGs.
Excluding that another genre could include the same means to deliver in their own genre.
So if a game includes a customization system, inventory management and the rest, it pushes it into the RPG genre by those players.
The idea of mixed genre is denying the evolution to a genre.
Why should story not be part of a shooter as a means to intensify the shooter experience?
Customization of character? present for ages.
Customization of weaponry? present for ages.
The big difference for the shooter genre is that the genre demands were answered by the technological progress in the right order: it matters more for a shooter to developp the correct detection algorithms that allow proper head shots and cover works than investing resources into developing a story.
Bioware brought their expertise in story telling to the shooter genre, and had to try over three games before having their customization stuff properly done.
The bulk of technological knowledge to put up a decent shooter was already acquired.