>I know how to fix this but I'm not "allowed to" can eat away at you easily.

This really is the worst, and that's why I left my first job. Funnily enough, I just took that job back after a few years but I am now the lead and sole developer on it, I'm having the time of my life doing what I've always wanted to do back then, and seeing the product now flourish.

The bad code didn't really matter, it was the fact that I was not allowed to improve it and forced to build new features on top of crappy code that made me quit in the first place.