Your job is to do what is being asked of you and not screw it up too much.
If they wanted to track requirements, they'd already track them.
People have very fragile egos - if you come in as a junior dev and start suggesting shit - they will not like that.
If you come in as a senior dev and start suggesting shit, they'll not like it, unless your suggestion is 'how about I do your work for you on top of my work, while you get most or all of the credit'.
That is the only suggestion most other people are interested in.
Source: been working for a while.