You are not a sucker. However, your experience is a very good illustration of the fact: Very often, folks who design and sell chicken coops really don't know what they are doing. Or IF THEY DO KNOW WHAT THEY ARE DOING, they are placing their pursuit of a tidy profit over providing a good product. Unfortunately, it's usually the first time chicken owners who are buying a pre-made coop, and they are depending on the seller to know how to build a good coop.
Kudos to you for listening to the advice you've received and beefing up your coop accordingly with hardware cloth (welded, not twisted wire) and installing a skirt. I can't tell you how often new folks on BYC post about a coop problem, yet refuse to listen to the advice they receive from seasoned flock keepers. They ask for advice, yet dismiss the advice, with the statement... "It will be fine... or the seller says... or The zoning code for my town says..."