I work with people where design is not seemed as a very important part when advertising products or events. I am, as far as I know, the only person with a professional graphic design education. It is really difficult for me to change something there, everytime I try to establish at least some simple guidelines. And many do not have a single clue about design, e.g. different colors every time, no need for a consistent design, even colors and fonts vary in each design that is made.
I thought that it is easier to convince these people to let a professional do it, I am happy to accept criticism, but I don't want to explain to people why you should't use a rainbow gradient as a background or why you should leave some margin between content and border. They simply do not care.
Normally when I try to convince a person, I look at the facts, but except for color theory and some design principles I learned at school, I've never seen and actual rules derived from studies or something. Like how can I explain to these people that white space is important. Every time I just want to say: "Because it just looks shit" but that doesn't work.
It's actually only a problem because now my colleagues are demanding some designs, and although they have no actual education and experience, tell me exactly which layout to use, even though it looks nothing like anything else we've done for that specific marketing campaign. Or they ask me to just remove the white space to fit more text into it.