I'm trying to stick to known/reputable sites so I don't run into something that's one step ahead of the anti-virus.
Since a large portion of infections come from legit websites being hacked, sticking with only "known/reputable sites (while a good practice) is not enough to protect you.
Why is there not a provision to submit this site so that it will have a negative reputation?
Because a sites infection status is not what WebRep (and by proxy, user input) is for....that is what the Web/Network Shields are for. Reporting infections via WebRep would result in a whole lot of unqualified people reporting things they do not even begin to understand.
WebRep currently has 2 facets. The first being user-input based reputation, based on like/dislike (colored green to red) and content type. The second being a filter for Phishing sites.