There were/are many elements that prevented the use of 'commonplace' from simply resulting in poetry that was/is dull and boring. The majority of commonplace writing consisted of poets picking common objects yes, but using them in a way that everyone could relate to these objects. They took the ordinary and made something out of it. The purpose really was to illustrate that even in the most common things we can find creativity. This concept is what is called defamiliarization or ostranenie.
Hope I helped! If you have any other questions or would like further explanation just let me know!! :)
Commonplace is something that everybody knows and do in the same way. That kind of tasks become boring and dull after some time. Indeed, commonplace refers to standard and ordinary situations, objects or concepts. The diversification and critique prevented the overuse of a commonplace. The poets applied their creativity and knowledge which gave birth to many different styles and movements. They made something out of something in a different way and the critiques shaped the way of rules and principles. The process is called ostranenie, which is a Russian word and means defamiliarization.
When someone stand by your side even when they shouldn't. For example, when you have an argument with someone but they are still willing to help you out before you have resolved.
Dictionary Definition:
giving or showing firm and constant support or allegiance to a person or institution
