I seriously don't understand the difference between god diamonds and ungodded ones because on sky block.net anyway people think that god diamonds are worthless, but you can still craft things with it.

These pictures show exactly what you can craft with god diamonds.
Can someone please tell me then why they are worthless?

 

I think it may be like that because they can't stack with regular diamonds.

 

That does make sense, but they can still be used.

 

Yes but they are perfered not.

 

Here's a tip. If you make a diamond block with any amount of normal/god diamonds (as long as its a total of 9 diamonds), it will become a diamond block then turn the diamond block back into 9 diamonds and all of them will be ungodded. so if you have 8 ungodded diamond and 1 godded diamond, you can make a diamond block and then turn the diamond block back into 9 diamonds and the 1 diamond that was godded will become ungodded. I don't know who told you they were worthless but they are completely the same.