Yep, I agree, I'm not sure where the OP got the impression that all poetry was clear and concise. In any case, what may not be "clear and concise" to one person, may be perfectly clear to someone else. Moreover, what are we to do when someone fails to understand a philosophical idea? Instantly dismiss it as being "overly complicated"?-of course not, philosophical thinking takes practice, and, for some, initially requires a lot of effort in order to learn how to think in unusual ways.
If someone rarely or never engages in philosophical thought, then they will come across ideas that appear alien to them, and they initially struggle to grasp new ideas. Contrast this with someone who engages in philosophy regularly, they will have become familiar with the process of getting to grips with new ideas, questioning their own ideas, and forming their own new ideas-that’s why philosophy is "difficult" for some people, because they simply do not engage in the processes of philosophy.
And then again, there are just some people who do not appear to be able to familiarise themselves with this process, and always struggle.