At any medium or large company, this is going to vary significantly between projects and teams. At a small company, shit code is more or less to be expected.
Software is a dirty job son. Now put your hazmat suit back on and back to scrubbing!
These seem like the kind of things you could/should be asking in your interview. For big companies, like levels.fyi caters to, there is no one size fits all answer. For small ones, the answer may be more straightforward, but you may have the ability to effect change for the better yourself.
That idea might be DOA. Every company I've been able to peek behind the tech curtain, it's bubble-gum and bailing-wire all the way down.