Earlier quoted context omitted.
> Choice example: does a time period "from January 2019 to January 2020" include two Januaries? The answer to this question would change, sometimes twice a week, when asked of the "product owner". Unfortunately, the only way you can protect yourself is to have a paper trail. If the PO says something, write it down in your tracker (Jira, Trello etc.), or at least an email. If the PO is unclear, write the answer accord…
Though even in a non toxic environment you should document any product decisions and why they were made. Your PM now could be the most amazing and helpful person in the world, but in 3 years it may be important to know if there is an important reason a time period from January to January includes both Januaries (and thus something important will stop working if you change it) or whether that was an arbitrary decision…
So, while I did spend a few months documenting all these issues, the company itself had not made room for engineering-led process improvements. Noticing that, I started spending political capital on trying to fix it, which is incredibly stressful, slow, and unrewarding work. After a few months of this, I finally came to my senses and realized that, this not being my company, I would not accrue any of the benefits of improving their processes. Time to leave.
The lesson, for me, has been to avoid working at companies that are either not product-focused (in which case engineering is just a cost-centre, having extremely low status within the organization), and to avoid stubbornly non-technical founders (i.e. any founder/owner who refuses to care about their engineering department beyond asking "is it done yet?").