At least where I work, it's hard to have passion given the fundamental issues with the codebase that there's never any time or money to address. It's like being on a ship pockmarked with holes and water coming in, that by all rights should be sinking, but is kept going by the endless pockets of our customers paying us to man the various pumps and keep the engines from flooding. And of course throw on new features that create yet more holes that there's no time or money to fix. However there's never any money to patch said holes, despite the buckets that get dumped on manning the pumps on a daily basis. The ship does something important, so you can take some pride in fulfilling the mission in spite of circumstances, but that tiny sliver of satisfaction is all there is.

If you're passionate about the mission/coding you will just produce a lot of impotent anger, because there's no way an IC is going to restructure the program given the layers of bureaucracy in the way. Maybe if you went management and then spent a decade or two climbing the corporate ladder, and even then you'll run into brand new managerial constraints. So if you're going to stick around, you learn to detach. It's one of the many reasons I plan to have a new job by Christmas :)