[WIP] Can I have a reality check?

My sibling mentioned that I have a lot of open spots between my stitches, probably by pulling too hard at the thread.

Perhaps the coverage of the black and dark green is not optimal (doesn't help that it's etoille as well), but is that not bound too happen when stitching on white?

So, could I actually improve things or is my sibling overly critical on something that is handmade?