Step back and draw a deep breath. Re-focus and now religiously document everything, runbooks, code comments, deployment guides, issues and outage reporting. Yo

Step back and draw a deep breath. Re-focus and now religiously document everything, runbooks, code comments, deployment guides, issues and outage reporting. You only get to encounter a new codebase once. While everyone else justs accepts things as they are, very few will ask why. Some of the senior devs won't even know why certain things are the way they are. By documenting everything, for yourself initially, you will over time gain both experience and get one over on the complacent senior devs. If a junior dev makes a mistake, it's more on the senior devs and managers to catch it, you're not expected to be supernaturally correct all the time coming into a situation with zero knowledge.