It's actually explained very clearly in the lore. After the fall of the republic clones weren't being made any more. The empire started recruiting normal humans to be stormtroopers. The empire did every thing with an iron grip, training was brutal but hurried so they could get ad many troops as possible. The empires strategy was to overwhelm with numbers, not beat their enemy with combat prowess. A majority of the troops were depressed and tired, not really knowing what they were fighting for.....I could go on and on

I'm pretty sure you're just bullshitting.