My phone slows down every time my device is updated. Why does this happen?

Every year new hardware comes out that is compatible with the new software release. Since you have older hardware, it is not built specifically for the software updates, causing the devices to slow down. The only way around this is to declutter your device or  replace the battery. Doing these few tricks you may notice a slight increase in speed, but not how your phone or device was working when you originally bought it.