While Appian as a whole is a great company to work for, the marketing department specifically is not a place to go if you are passionate about your career. Unless you are just looking for a paycheck / benefits and have high tolerance for a lot of change, you won't last long here. From a digital marketing perspective, they still operate like it's 2010, so you won't go in, and learn about the latest in B2B marketing.
The culture in marketing is also toxic. While on the surface level, the culture is collegial and laid back, there's an intensity they expect you to operate under that was too much for me. It comes all the way down from the Founders. Ultimately, I quit because I wasn't learning anything that was helping me grow my career. I didn't want to deal with the bureaucracy and lack of leadership/vision. Some of the people in leadership positions have questionable character but again, as long as you're in the 'cool club', no number of HR complaints will slow you down.