This reads like someone who has never worked on anything. Here's something I totally made up but have experienced half a dozen times and caused it the other half dozen:

Come in to an exciting new opportunity. The first week you recoil in horror the technical debt. It appears the previous maintainer/builder didn't know one or more of: basic system admin, testing, documentation, packages, coding design, database design, or security.

The incidents start. The code is so interdependent it's terrifying to make even a small change. Fixing a bug in their custom json generator breaks a service you don't know exists and takes out billing. Yes they wrote their own. You lose the confidence of the team already there. Now you are too afraid to make changes.

All you can do is toil or try to think about selling a rewrite. When one or both of those hit burn out you fire up LinkedIn and beg for mercy.