As a metal bass player myself, I just wanted to give my thoughts on this. I apologize if it kinda "goes off the deep end."
First, I really enjoy metal music overall but yes, there are certain styles of it that are rather boring to me. I enjoy the bands where the bass player has a voice and does their own "versions" of songs. But, there are times where the bass needs to just hang back and double up on the guitars. The best way I see that style of metal is like jazz.
From personal experience, touring and recording/whatnot, there has to be a balance. But the kicker is that some bass players don't want to put in the time or effort to really expand on a song, and that's fine. You will find SO many metal bands that the bass player is just a copy of the guitars, minus the solos and whatnot but that's fine. I have been fortunate enough to have band members that allow me to do what I want to do. So as for you, I would say talk to them and present some ideas. If they shoot them down then so be it. That's why there is solo music.
My brother told me once that, when I was first starting to play bass guitar, that there is a time and place for everything in music. My first band shot down most of my ideas, mainly because I was the new guy. But later on, they became more comfortable with allowing me to do my thing. The main point what I'm trying to get across ( poorly) is that do what you love. If you enjoy playing with the band and they don't want you to do things outside of the box, either quit or keep playing and work with another band/write your own music.
One final thing is that sometimes, not doubling up on the guitars and playing a even more basic version of a guitar riff is very cool at times as well. Cynic comes to mind. Sean Malone is amazing. He can do things outside of the box by either doing some amazing yet crazy parts or even hanging back with a more deconstructed riff on the bass and still sound amazing.
Give it time with the band. Talk to them, show them some examples and in the meantime, keep practicing. If you come up with some ideas that the band shoots down, make your own music with it. And have fun!