Designers become better by learning certain theories and nuances of logo design over time, and using these learnings as they produce designs. However, a human can only retain and regularly access so much knowledge. Artificial intelligence, on the other hand, has no limit of how much it can learn and frequently access.
There’s also the question of experience. A designer purely focused on branding will design about 20 logos a year. An AI can design a million without skipping a beat. That’s a million more learning experiences. A million more chances for the AI entity to learn what customers want.
AI has the capability to learn more than a traditional designer, and at a much faster pace due to the sheer number of logos that it can work with.