I’d try to drop requirement 3. Any insights made could be beneficial to somebody else working on the code (especially in closed-source environments only touched by people employed by your organization).

Re: critical tone, instead of saying “this is a useless garbage fire” maybe something like “it is not yet apparent how this interacts with blah blah.” There’s always a way to phrase it where it’ll plant the seeds of how you want the reader to feel about it without being overt.

My 2c, anyway.