I'm not really proposing anything or even asking a question, I just felt this should be pointed out.
Seems to me the question is very straight forward and answerable.
I suspect this is something to do with how you phrased it as "how do you do x?" Perhaps a less subjective title would be "How to delete a plan from Microsoft Planner?"
The question is straightforward and answerable as you have proven. It's just the title could, to a robot or when read out loud with a weird rising inflection on the word "you", sound like you are canvassing for opinion rather than a solid answer.