While a significant part of my work used to focus on creating the design itself, with the rise of AI my role has shifted much closer to that of an art director. The only difference is that the designer working under me is AI.
AI produces the first versions, and I review them, correct them, change the direction, adjust the composition, and decide what is worth developing further.
Before, I could spend most of the available time polishing two options. Now, in the same time, I can look through four, six, or eight iterations, take the strongest ideas from them, and then bring the final two options to the same level of polish.
In marketing agencies, timelines rarely expand just because the design needs more work. The launch date stays where it is, while the time available for exploration gets compressed.
So yes, marketing agencies benefit from AI. Designers in B2B agencies benefit too. But clients probably benefit the most. Not because they receive more options, but because the options they do receive have already gone through a much broader selection process.