Everyone seems to come out pretty badly from this story. The client clearly isn't good at working with people. As noted by controlledchaos the author isn't go

Everyone seems to come out pretty badly from this story. The client clearly isn't good at working with people. As noted by controlledchaos the author isn't good at working with clients, communicating complexity is hard to do but it's essential to work through this with a client. It can be very frustrating and takes a lot of time but just stating that you're an expert is never going to win anyone over. You have to demonstrate that fact to them and understand their goals and motivations. The author's boss sucks, he basically threw the author to the wolves and only stepped in at the last minute by which time it was too late. The senior developer's advice to not care is toxic.