Hey Keanichii! That's some great reflection- spending too much time on the concept and not enough time preparing on how to present that concept is tough to balance. I made a similar mistake of not spending enough time preparing for the presentation, which led to the listeners not being able to share the same vision as the creator :(
It's nice that your group decided to give everyone a second opportunity to pitch your game ideas to each other, and even if your concept didn't get chosen you can always take some ideas from it and merge them into the chosen game!