The 8 can take amazing images.
Use microfiber cloth on lens before a shot.
Try to hold phone steady and press lightly.
Apps like Snapseed, Lightroom & even stock Photos app can help with editing.
Anyway to the OP, clean the lens and ensur you tap on the subject you want to take a photo off so it focuses properly, during my time with the 8 I found the photos were poor but tapping on the subject resolved that and it took great photos after.