This is an excellent question! The way TubeBuddy works is we take al look at the traffic data for viewers and rank that based on how many people are searching for that keyword, how many people are already making videos for that keyword, and how well optimized your channel is for that keyword.
When you get a Poor rank we are telling you that there is either a lot of competition, not very much traffic, you aren't optimized very well for that keyword and or various combinations of each. It really has nothing to do with you or your video, so much as it is a reflection of the current overall traffic for that keyword.
You can definitely rank for keywords that are deemed poor... you simply have to beat out the competition. Now, if the keyword is poor due to search volume it isn't difficult to beat out what competition there may be and rank. If there is a lot of heavy competition for a keyword it is going to be far more difficult to rank. But to do so you simply need to beat out the competition. That isn't easy, but it can be done.
For us smaller creators these keyword rankings are invaluable because it gives us the ability to research what people are searching for and what terms are being underserved. It allows us to select specific topics to gain the views needed in order to work our way up in the ranks and get views even when we are just starting.