Some legit vendors have shoddy websites, yes. Many scammers have professional websites. So that's not a great way of judging.
Yep, one of the best sources I know stocks lots of illegals that I've been unable to find anywhere else, and their site looks like something a 10 year old could knock up in a wysiwyg html editor. Some of the most professional looking sites are some of the worst sites/biggest scams. Vendor review sites are your friend