Designers are blind to their own flaws.

Onur Cobanli ཡིས་འགྲེལ་བཤད་བརྗོད་པ།
It is challenging for designers to identify shortcomings in their own work, which makes external feedback invaluable. It is really hard to see faults in your own work, your own design. Thus, many designers never see wrong in their designs, but quickly notice errors by that of others. Mutual constructive criticism is invaluable as designers easily spot others' mistakes. By engaging in constructive critique with peers, designers can gain insights into aspects of their work they might have missed, ultimately leading to better and more self-aware creations. And very rarely, make friends because let's be real, no designer likes critique.