The user interface is your product's face
An easier website is just one click away. Your customers do not want to feel stupid when using your product. They will not read the comprehensive manual you've written. They'll think you were unwilling to take their needs into account if they think they have to read the manual in advance. They do not want to register on your website, they just want to do some shopping or browse your offering.
Even if user-centric design (UCD) is not a familiar term, you've most likely utilized its way of thinking and definitely have enjoyed its results. The core idea of UCD is to keep the focus on the user. As Google principles say, "Focus on the user and all else will follow."