I think a frontend engineer needs to have both a very strong aesthetic design ability as well as engineering abilities. Marketing on the other hand is a different animal. A good marketer can sell bad code, U/X.

I worked in QA and I think this is similar. The best QA testers aren’t engineers because they don’t make assumptions. Marketers make assumptions but not about code but about human behavior like you said but I think this relates more to the U/X and marketing relationship vs the engineer to U/X relationship.