A good paper probably does not need a conclusion because if the paper is well written, the conclusion should be clear to the reader. Short papers develop incisive writing. Long papers often ramble. Require a short paper. The introduction is a key source of procrastination and should be written last.
Ideas evolve with writing.
Writing is a thinking tool. Introductions and conclusions also evolve and should be written last to save time and frustration. A reader presented with data and no explanation or development will nearly always reach a conclusion different than the writers. Lead the reader through the data to the point. Every paragraph should have a clear transition that looks back to the previous paragraph and forward to the coming idea.