1. A friend of mine came up with a formula for motivation at work that you can say in one sentence. I love it because it's both simple and powerful: "People want to be a significant member of a winning team on an inspiring mission." You want to feel that you matter. You want to feel you have a chance at success. You wan't to feel your work makes a difference.
Trouble comes when any of those needs aren't met. It sounds like you don't feel that you are allowed to significantly contribute and it sounds like you don't feel your team is set up for success. I don't know if you would ever be inspired by the company's mission. In my experience, no amount of salary will ever compensate for the absence of any of the three above.
2. Even in a job that meets all three of those needs, motivation waxes and wanes. Work that matters is always challenging and you go through streaks and slumps. Here's something I've learned that's interesting and really freeing: Forget the insane amount of ink that's been dedicated to motivational coaching and repeat this: "You don't have to be motivated to start." You just don't. Set a timer for 30 minutes, set the existential stuff aside for a moment (it feels really good), and start. Just 30 minutes. This is powerful because you'll see the chicken and the egg of it all: Sometimes you are motivated to start. But sometimes starting in makes you motivated. (I'm amazed at how often I ignore the timer going off at the end and just keep working.)
Good luck with it! I hope you find your purpose and satisfaction. The big money is nice while you can get it, but it never serves as a replacement involvement in real, meaningful work.