Each node connects to 8 nodes, and each of these 8 nodes connect to another 8 nodes, and so on. But some of these connections are duplicated, so it will take several hop before a block is relayed to majority of the nodes, 4-5 hops maybe. When you have 8 seconds for a block transfer and the block verify time of 8 seconds, the nodes on the far end of the network would receive it in 80 seconds, which is a significant delay

Let's first imagine the ideal bitcoin blockchain done by aliens: It takes 1 second to receive and verify each block, takes 1MB hard drive space, and can carry unlimited amount of transactions in 10 minutes    Then you add those real world limitations on it and see which part you can compromise